US 5,889,174 AGrant
Nucleotide Sequences Encoding Pesticidal Proteins
Issue Date:1999-03-30
•11 Claims
•1 Drawing Sheets
Abstract
The present invention is drawn to pesticidal strains and proteins. Bacillus strains which are capable of producing pesticidal proteins and auxiliary proteins during vegetative growth are provided. Also provided are the purified proteins, nucleotide sequences encoding the proteins and methods for using the strains, proteins and genes for controlling pests.
Metadata
Assignee
- Novartis Finance Corporation
Inventors
- Gregory W. Warren
- Michael G. Koziel
- Martha A. Mullins
- Gordon J. Nye
- Brian Carr
- Nalini M. Desai
- Kristy Kostichka
- Juan J. Estruch
Application Information
Application Number:US 470567&
Filing Date:1995-06-06
Priority Date:1993-03-25
Art Unit:166
Classifications
IPC:
C12N 1531C12P 2102C07K 1432
Field of Search:
43553669.123.7;23.71
Patent Drawings (1 sheets)
Description
FIELD OF THE INVENTION
The present invention is drawn to methods and compositions for controlling plant and non-plant pests.
BACKGROUND OF THE INVENTION
Insect pests are a major factor in the loss of the world's commercially important agricultural crops. Broad spectrum chemical pesticides have been used extensively to control or eradicate pests of agricultural importance. There is, however, substantial interest in developing effective alternative pesticides.
Microbial pesticides have played an important role as alternatives to chemical pest control. The most extensively used microbial product is based on the bacterium Bacillus thuringiensis (Bt). Bt is a gram-positive spore forming Bacillus which produces an insecticidal crystal protein (ICP) during sporulation.
Numerous varieties of Bt are known that produce more than 25 different but related ICP's. The majority of ICP's made by Bt are toxic to larvae of certain insects in the orders Lepidoptera, Diptera and Coleoptera. In general, when an ICP is ingested by a susceptible insect the crystal is solubilized and transformed into a toxic moiety by the insect gut proteases. None of the ICP's active against coleopteran larvae such as Colorado potato beetle (Leptinotarsa decemlineata) or Yellow mealworm (Tenebrio molitor) have demonstrated significant effects on members of the genus Diabrotica particularly Diabrotica virgifera virgifera, the western corn rootworm (WCRW) or Diabrotica longicornis barberi, the northern corn rootworm.
Bacillus cereus (Bc) is closely related to Bt. A major distinguishing characteristic is the absence of a parasporal crystal in Bc. Bc is a widely distributed bacterium that is commonly found in soil and has been isolated from a variety of foods and drugs. The organism has been implicated in the spoilage of food.
Although Bt has been very useful in controlling insect pests, there is a need to expand the number of potential biological control agents.
BRIEF DESCRIPTION OF THE FIGURE
FIG. 1: Characterization of pCIB6022. Boxed regions represent the extent of VIP1A(a) and VIP2A(a). White box represents the portion of VIP1 encoding the 80 kDa peptide observed in Bacillus. Dark box represents the N-terminal `propeptide` of VIP1A(a) predicted by DNA sequence analysis. Stippled box represents the VIP2A(a) coding region. Large `X` represents the location of the frameshift mutation introduced into VIP1A(a). Arrows represent constructs transcribed by the beta-galactosidase promoter. Restriction Sites: C-Cla I; X-Xba I; S-Sca I; RI-Eco RI; B-Bgl II; RV-Eco RV.
SUMMARY OF THE INVENTION
The present invention is drawn to compositions and methods for controlling plant and non-plant pests. Particularly, new pesticidal proteins are disclosed which are isolatable from the vegetative growth stage of Bacillus. Bacillus strains, proteins, and genes encoding the proteins are provided.
The methods and compositions of the invention may be used in a variety of systems for controlling plant and non-plant pests.
DETAILED DESCRIPTION OF THE INVENTION
Compositions and methods for controlling plant pests are provided. In particular, novel pesticidal proteins are provided which are produced during vegetative growth of Bacillus strains. The proteins are useful as pesticidal agents.
The present invention recognizes that pesticidal proteins are produced during vegetative growth of Bacillus strains. To date, all of the identified pesticidal proteins of the invention are secreted from the cell. Prior to the present invention, there was no recognition in the art that a class or classes of pesticidal proteins are produced during vegetative growth of Bacillus. The only report was of a single mosquitocidal toxin from Bacillus sphaericus SSII-1 by Myers and Yousten in Infect. Immun., 19:1047-1053 (1978). Having recognized that such a class exists, the present invention embraces all vegetative insecticidal proteins, hereinafter referred to as VIPs, except for the mosquitocidal toxin from B. sphaericus.
The present VIPs are not abundant after sporulation and are particularly expressed during log phase growth before stationary phase. For the purpose of the present invention vegetative growth is defined as that period of time before the onset of sporulation. Genes encoding such VIPs can be isolated, cloned and transformed into various delivery vehicles for use in pest management programs.
For purposes of the present invention, pests include but are not limited to insects, fungi, bacteria, nematodes, mites, ticks, protozoan pathogens, animal-parasitic liver flukes, and the like. Insect pests include insects selected from the orders Coleoptera, Diptera, Hymenoptera, Lepidoptera, Mallophaga, Homoptera, Hemiptera, Orthroptera, Thysanoptera, Dermaptera, Isoptera, Anoplura, Siphonaptera, Trichoptera, etc., particularly Coleoptera and Lepidoptera.
Tables 1-10 gives a list of pests associated with major crop plants and pests of human and veterinary importance. Such pests are included within the scope of the present invention.
Now that it has been recognized that pesticidal proteins can be isolated from the vegetative growth phase of Bacillus, other strains can be isolated by standard techniques and tested for activity against particular plant and non-plant pests. Generally Bacillus strains can be isolated from any environmental sample, including soil, plant, insect, grain elevator dust, and other sample material, etc., by methods known in the art. See, for example, Travers et al. (1987) Appl. Environ. Microbiol. 53:1263-1266; Saleh et al. (1969) Can J. Microbiol. 15:1101-1104; DeLucca et al. (1981) Can. J. Microbiol. 27:865-870; and Norris, et al. (1981) "The genera Bacillus and Sporolactobacillus," In Starr et al. (eds.), The Prokaryotes: A Handbook on Habitats, Isolation, and Identification of Bacteria, Vol. II, Springer-Verlog Berlin Heidelberg. After isolation, strains can be tested for pesticidal activity during vegetative growth. In this manner, new pesticidal proteins and strains can be identified.
Such Bacillus microorganisms which find use in the invention include Bacillus cereus and Bacillus thuringiensis, as well as those Bacillus species listed in Table 11.
In accordance with the present invention, the pesticidal proteins produced during vegetative growth can be isolated from Bacillus. In one embodiment, insecticidal proteins produced during vegetative growth, can be isolated. Methods for protein isolation are known in the art. Generally, proteins can be purified by conventional chromatography, including gel-filtration, ion-exchange, and immunoaffinity chromatography, by high-performance liquid chromatography, such as reversed-phase high-performance liquid chromatography, ion-exchange high-performance liquid chromatography, size-exclusion high-performance liquid chromatography, high-performance chromatofocusing and hydrophobic interaction chromatography, etc., by electrophoretic separation, such as one-dimensional gel electrophoresis, two-dimensional gel electrophoresis, etc. Such methods are known in the art. See for example Current Protocols in Molecular Biology, Vols. 1 and 2, Ausubel et al. (eds.), John Wiley & Sons, NY (1988). Additionally, antibodies can be prepared against substantially pure preparations of the protein. See, for example, Radka et al. (1983) J. Immunol. 128:2804; and Radka et al. (1984) Immunogenetics 19:63. Any combination of methods may be utilized to purify protein having pesticidal properties. As the protocol is being formulated, pesticidal activity is determined after each purification step.
Such purification steps will result in a substantially purified protein fraction. By "substantially purified" or "substantially pure" is intended protein which is substantially free of any compound normally associated with the protein in its natural state. "Substantially pure" preparations of protein can be assessed by the absence of other detectable protein bands following SDS-PAGE as determined visually or by densitometry scanning. Alternatively, the absence of other amino-terminal sequences or N-terminal residues in a purified preparation can indicate the level of purity. Purity can be verified by rechromatography of "pure" preparations showing the absence of other peaks by ion exchange, reverse phase or capillary electrophoresis. The terms "substantially pure" or "substantially purified" are not meant to exclude artificial or synthetic mixtures of the proteins with other compounds. The terms are also not meant to exclude the presence of minor impurities which do not interfere with the biological activity of the protein, and which may be present, for example, due to incomplete purification.
Once purified protein is isolated, the protein, or the polypeptides of which it is comprised, can be characterized and sequenced by standard methods known in the art. For example, the purified protein, or the polypeptides of which it is comprised, may be fragmented as with cyanogen bromide, or with proteases such as papain, chymotrypsin, trypsin, lysyl-C endopeptidase, etc. (Oike et al. (1982) J. Biol. Chem. 257:9751-9758; Liu et al. (1983) Int. J. Pept. Protein Res. 21:209-215). The resulting peptides are separated, preferably by HPLC, or by resolution of gels and electroblotting onto PVDF membranes, and subjected to amino acid sequencing. To accomplish this task, the peptides are preferably analyzed by automated sequenators. It is recognized that N-terminal, C-terminal, or internal amino acid sequences can be determined. From the amino acid sequence of the purified protein, a nucleotide sequence can be synthesized which can be used as a probe to aid in the isolation of the gene encoding the pesticidal protein.
It is recognized that the pesticidal proteins may be oligomeric and will vary in molecular weight, number of protomers, component peptides, activity against particular pests, and in other characteristics. However, by the methods set forth herein, proteins active against a variety of pests may be isolated and characterized.
Once the purified protein has been isolated and characterized it is recognized that it may be altered in various ways including amino acid substitutions, deletions, truncations, and insertions. Methods for such manipulations are generally known in the art. For example, amino acid sequence variants of the pesticidal proteins can be prepared by mutations in the DNA. Such variants will possess the desired pesticidal activity. Obviously, the mutations that will be made in the DNA encoding the variant must not place the sequence out of reading frame and preferably will not create complementary regions that could produce secondary mRNA structure. See, EP Patent Application Publication No. 75,444.
In this manner, the present invention encompasses the pesticidal proteins as well as components and fragments thereof. That is, it is recognized that component protomers, polypeptides or fragments of the proteins may be produced which retain pesticidal activity. These fragments include truncated sequences, as well as N-terminal, C-terminal, internal and internally deleted amino acid sequences of the proteins.
Most deletions, insertions, and substitutions of the protein sequence are not expected to produce radical changes in the characteristics of the pesticidal protein. However, when it is difficult to predict the exact effect of the substitution, deletion, or insertion in advance of doing so, one skilled in the art will appreciate that the effect will be evaluated by routine screening assays.
The proteins or other component polypeptides described herein may be used alone or in combination. That is, several proteins may be used to control different insect pests.
Some proteins are single polypeptide chains while many proteins consist of more than one polypeptide chain, i.e., they are oligomeric. Additionally, some VIPs are pesticidally active as oligomers. In these instances, additional protomers are utilized to enhance the pesticidal activity or to activate pesticidal proteins. Those protomers which enhance or activate are referred to as auxiliary proteins. Auxiliary proteins activate or enhance a pesticidal protein by interacting with the pesticidal protein to form an oligomeric protein having increased pesticidal activity compared to that observed in the absence of the auxiliary protein.
Auxiliary proteins activate or increase the activity of pesticidal proteins such as the VIP1 protein from AB78. Such auxiliary proteins are exemplified by, but not limited to, the VIP2 protein from AB78. As demonstrated in the Experimental section of the application, auxiliary proteins can activate a number of pesticidal proteins. Thus, in one embodiment of the invention, a plant, Parent 1, can be transformed with an auxiliary protein. This Parent 1 can be crossed with a number of Parent 2 plants transformed with one or more pesticidal proteins whose pesticidal activities are activated by the auxiliary protein.
The pesticidal proteins of the invention can be used in combination with Bt endotoxins or other insecticidal proteins to increase insect target range. Furthermore, the use of the VIPs of the present invention in combination with Bt .delta.-endotoxins or other insecticidal principles of a distinct nature has particular utility for the prevention and/or management of insect resistance. Other insecticidal principles include protease inhibitors (both serine and cysteine types), lectins, .alpha.-amylase and peroxidase. In one preferred embodiment, expression of VIPs in a transgenic plant is accompanied by the expression of one or more Bt .delta.-endotoxins. This co-expression of more than one insecticidal principle in the same transgenic plant can be achieved by genetically engineering a plant to contain and express all the genes necessary. Alternatively, a plant, Parent 1, can be genetically engineered for the expression of VIPs. A second plant, Parent 2, can be genetically engineered for the expression of Bt .delta.-endotoxin. By crossing Parent 1 with Parent 2, progeny plants are obtained which express all the genes introduced into Parents 1 and 2. Particularly preferred Bt .delta.-endotoxins are those disclosed in U.S. application Ser. No. 07/951,715, herein incorporated by reference.
A substantial number of cytotoxic proteins, though not all, are binary in action. Binary toxins typically consist of two protein domains, one called the A domain and the other called the B domain (see Sourcebook of Bacterial Protein Toxins. J. E. Alouf and J. H. Freer eds.(1991) Academic Press). The A domain possesses a potent cytotoxic activity. The B domain binds an external cell surface receptor before being internalized. Typically, the cytotoxic A domain must be escorted to the cytoplasm by a translocation domain. Often the A and B domains are separate polypeptides or protomers, which are associated by a protein-protein interaction or a di-sulfide bond. However, the toxin can be a single polypeptide which is proteolytically processed within the cell into two domains as in the case for Pseudomonas exotoxin A. In summary binary toxins typically have three important domains, a cytotoxic A domain, a receptor binding B domain and a translocation domain. The A and B domain are often associated by protein-protein interacting domains.
The receptor binding domains of the present invention are useful for delivering any protein, toxin, enzyme, transcription factor, nucleic acid, chemical or any other factor into target insects having a receptor recognized by the receptor binding domain of the binary toxins described in this patent. Similarly, since binary toxins have translocation domains which penetrate phosopholipid bilayer membranes and escort cytotoxins across those membranes, such translocation domains may be useful in escorting any protein, toxin, enzyme, transcription factor, nucleic acid, chemical or any other factor across a phospholipid bilayer such as the plasma membrane or a vesicle membrane. The translocation domain may itself perforate membranes, thus having toxic or insecticidal properties. Further, all binary toxins have cytotoxic domains; such a cytotoxic domain may be useful as a lethal protein, either alone or when delivered into any target cell(s) by any means.
Finally, since binary toxins comprised of two polypeptides often form a complex, it is likely that there are protein-protein interacting regions within the components of the binary toxins of the invention. These protein-protein interacting domains may be useful in forming associations between any combination of toxins, enzymes, transcription factors, nucleic acids, antibodies, cell binding moieties, or any other chemicals, factors, proteins or protein domains.
Toxins, enzymes, transcription factors, antibodies, cell binding moieties or other protein domains can be fused to pesticidal or auxiliary proteins by producing in frame genetic fusions which, when translated by ribosomes, would produce a fusion protein with the combined attributes of the VIP and the other component used in the fusion. Furthermore, if the protein domain fused to the VIP has an affinity for another protein, nucleic acid, carbohydrate, lipid, or other chemical or factor, then a three-component complex can be formed. This complex will have the attributes of all of its components. A similar rationale can be used for producing four or more component complexes. These complexes are useful as insecticidal toxins, pharmaceuticals, laboratory reagents, and diagnostic reagents, etc. Examples where such complexes are currently used are fusion toxins for potential cancer therapies, reagents in ELISA assays and immunoblot analysis.
One strategy of altering pesticidal or auxiliary proteins is to fuse a 15-amino-acid "S-tag" to the protein without destroying the insect cell binding domain(s), translocation domains or protein-protein interacting domains of the proteins. The S-tag has a high affinity (K.sub.d =10.sup.-9 M) for a ribonuclease S-protein, which, when bound to the S-tag, forms an active ribonuclease (See F. M. Richards and H. W. Wyckoff (1971) in "The Enzymes", Vol. IV (Boyer, P. D. ed.). pp. 647-806. Academic Press, New York). The fusion can be made in such a way as to destroy or remove the cytotoxic activity of the pesticidal or auxiliary protein, thereby replacing the VIP cytotoxic activity with a new cytotoxic ribonuclease activity. The final toxin would be comprised of the S-protein, a pesticidal protein and an auxiliary protein, where either the pesticidal protein or the auxiliary protein is produced as translational fusions with the S-tag. Similar strategies can be used to fuse other potential cytotoxins to pesticidal or auxiliary proteins including (but not limited to) ribosome inactivating proteins, insect hormones, hormone receptors, transcription factors, proteases, phosphatases, Pseudomonas exotoxin A, or any other protein or chemical factor that is lethal when delivered into cells. Similarly, proteins can be delivered into cells which are not lethal, but might alter cellular biochemistry or physiology.
The spectrum of toxicity toward different species can be altered by fusing domains to pesticidal or auxiliary proteins which recognize cell surface receptors from other species. Such domains might include (but are not limited to) antibodies, transferrin, hormones, or peptide sequences isolated from phage displayed affinity selectable libraries. Also, peptide sequences which are bound to nutrients, vitamins, hormones, or other chemicals that are transported into cells could be used to alter the spectrum of toxicity. Similarly, any other protein or chemical which binds a cell surface receptor or the membrane and could be internalized might be used to alter the spectrum of activity of VIP 1 and VIP2.
The pesticidal proteins of the present invention are those proteins which confer a specific pesticidal property. Such proteins may vary in molecular weight, having component polypeptides at least a molecular weight of 30 kDa or greater, preferably about 50 kDa or greater.
The auxiliary proteins of the invention may vary in molecular weight, having at least a molecular weight of about 15 kDa or greater, preferably about 20 kDa or greater; more preferably, about 30 kDa or greater. The auxiliary proteins themselves may have component polypeptides.
It is possible that the pesticidal protein and the auxiliary protein may be components of a multimeric, pesticidal protein. Such a pesticidal protein which includes the auxiliary proteins as one or more of its component polypeptides may vary in molecular weight, having at least a molecular weight of 50 kDa up to at least 200 kDa, preferably about 100 kDa to 150 kDa.
An auxiliary protein may be used in combination with the pesticidal proteins of the invention to enhance activity or to activate the pesticidal protein. To determine whether the auxiliary protein will affect activity, the pesticidal protein can be expressed alone and in combination with the auxiliary protein and the respective activities compared in feeding assays for pesticidal activity.
It may be beneficial to screen strains for potential pesticidal activity by testing activity of the strain alone and in combination with the auxiliary protein. In some instances an auxiliary protein in combination with the native proteins of the strains yields pesticidal activity where none is seen in the absence of an auxiliary protein.
The auxiliary protein can be modified, as described above, by various methods known in the art. Therefore, for purposes of the invention, the term "Vegetative Insecticidal Protein" (VIP) encompasses those proteins produced during vegetative growth which alone or in combination can be used for pesticidal activity. This includes pesticidal proteins, auxiliary proteins and those proteins which demonstrate activity only in the presence of the auxiliary protein or the polypeptide components of these proteins.
It is recognized that there are alternative methods available to obtain the nucleotide and amino acid sequences of the present proteins. For example, to obtain the nucleotide sequence encoding the pesticidal protein, cosmid clones, which express the pesticidal protein, can be isolated from a genomic library. From larger active cosmid clones, smaller subclones can be made and tested for activity. In this manner, clones which express an active pesticidal protein can be sequenced to determine the nucleotide sequence of the gene. Then, an amino acid sequence can be deduced for the protein. For general molecular methods, see, for example, Molecular Cloning, A Laboratory Manual, Second Edition, Vols. 1-3, Sambrook et al. (eds.) Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y. (1989), and the references cited therein.
The present invention also encompasses nucleotide sequences from organisms other than Bacillus, where the nucleotide sequences are isolatable by hybridization with the Bacillus nucleotide sequences of the invention. Proteins encoded by such nucleotide sequences can be tested for pesticidal activity. The invention also encompasses the proteins encoded by the nucleotide sequences. Furthermore, the invention encompasses proteins obtained from organisms other than Bacillus wherein the protein cross-reacts with antibodies raised against the proteins of the invention. Again the isolated proteins can be assayed for pesticidal activity by the methods disclosed herein or others well-known in the art.
Once the nucleotide sequences encoding the pesticidal proteins of the invention have been isolated, they can be manipulated and used to express the protein in a variety of hosts including other organisms, including microorganisms and plants.
The pesticidal genes of the invention can be optimized for enhanced expression in plants. See, for example U.S. application Ser. No. 07/951,715; EPA 0359472; EPA 0385962; WO 91/16432; Perlak et al. (1991) Proc. Natl. Acad. Sci. USA 88:3324-3328; and Murray et al. (1989) Nucleic Acids Research 17:477-498. In this manner, the genes can be synthesized utilizing plant preferred codons. That is the preferred codon for a particular host is the single codon which most frequently encodes that amino acid in that host. The maize preferred codon, for example, for a particular amino acid may be derived from known gene sequences from maize. Maize codon usage for 28 genes from maize plants is found in Murray et al. (1989), Nucleic Acids Research 17:477-498, the disclosure of which is incorporated herein by reference. Synthetic genes can also be made based on the distribution of codons a particular host uses for a particular amino acid.
In this manner, the nucleotide sequences can be optimized for expression in any plant. It is recognized that all or any part of the gene sequence may be optimized or synthetic. That is, synthetic or partially optimized sequences may also be used.
In like manner, the nucleotide sequences can be optimized for expression in any microorganism. For Bacillus preferred codon usage, see, for example U.S. Pat. No. 5,024,837 and Johansen et al. (1988) Gene 65:293-304.
Methodologies for the construction of plant expression cassettes as well as the introduction of foreign DNA into plants are described in the art. Such expression cassettes may include promoters, terminators, enhancers, leader sequences, introns and other regulatory sequences operably linked to the pesticidal protein coding sequence. It is further recognized that promoters or terminators of the VIP genes can be used in expression cassettes.
Generally, for the introduction of foreign DNA into plants Ti plasmid vectors have been utilized for the delivery of foreign DNA as well as direct DNA uptake, liposomes, electroporation, micro-injection, and the use of microprojectiles. Such methods had been published in the art. See, for example, Guerche et al., (1987) Plant Science 52:111-116; Neuhause et al., (1987) Theor. Appl. Genet. 75:30-36; Klein et al., (1987) Nature 327:70-73; Howell et al., (1980) Science 208:1265; Horsch et al., (1985) Science 227:1229-1231; DeBlock et al., (1989) Plant Physiology 91:694-701; Methods for Plant Molecular Biology (Weissbach and Weissbach, eds.) Academic Press, Inc. (1988); and Methods in Plant Molecular Biology (Schuler and Zielinski, eds.) Academic Press, Inc. (1989). See also US patent application Ser. No. 08/008,374 herein incorporated by reference. See also, EPA 0193259 and EPA 0451878A1. It is understood that the method of transformation will depend upon the plant cell to be transformed.
It is further recognized that the components of the expression cassette may be modified to increase expression. For example, truncated sequences, nucleotide substitutions or other modifications may be employed. See, for example Perlak et al. (1991) Proc. Natl. Acad. Sci. USA 88:3324-3328; Murray et al., (1989) Nucleic Acids Research 17:477498; and WO 91/16432.
The construct may also include any other necessary regulators such as terminators, (Guerineau et al., (1991), Mol. Gen. Genet., 226:141-144; Proudfoot, (1991), Cell, 64:671-674; Sanfacon et al., (1991), Genes Dev., 5:141-149; Mogen et al., (1990), Plant Cell, 2:1261-1272; Munroe et al., (1990), Gene, 91:151-158; Ballas et al et al., (1989), Nucleic Acids Res., 17:7891-7903; Joshi et al., (1987), Nucleic Acid Res., 15:9627-9639); plant translational consensus sequences (Joshi, C. P., (1987), Nucleic Acids Research, 15:6643-6653), introns (Luehrsen and Walbot, (1991), Mol. Gen. Genet., 225:81-93) and the like, operably linked to the nucleotide sequence. It may be beneficial to include 5' leader sequences in the expression cassette construct. Such leader sequences can act to enhance translation. Translational leaders are known in the art and include:
Picornavirus leaders, for example, EMCV leader (encephalomyocarditis 5' noncoding region) (Elroy-Stein, O., Fuerst, T. R., and Moss, B. (1989) PNAS USA 86:6126-6130);
Potyvirus leaders, for example, TEV leader (Tobacco Etch Virus) (Allison et al., (1986); MDMV leader (Maize Dwarf Mosaic Virus); Virology, 154:9-20), and
Human immunoglobulin heavy-chain binding protein (BiP), (Macejak, D. G., and Sarnow, P., (1991), Nature, 353:90-94;
Untranslated leader from the coat protein mRNA of alfalfa mosaic virus (AMV RNA 4), (Jobling, S. A., and Gehrke, L., (1987), Nature, 325:622-625;
Tobacco mosaic virus leader (TMV), (Gallie, D. R. et al., (1989), Molecular Biology of RNA pages 237-256; and
Maize Chlorotic Mottle Virus leader (MCMV) (Lommel, S. A. et al., (1991), Virology, 81:382-385. See also, Della-Cioppa et al., (1987), Plant Physiology, 84:965-968.
A plant terminator may be utilized in the expression cassette. See, Rosenberg et al., (1987), Gene, 56:125; Guerineau et al., (1991), Mol. Gen. Genet., 226:141-144; Proudfoot, (1991), Cell, 64:671-674; Sanfacon et al., (1991), Genes Dev., 5:141-149; Mogen et al., (1990), Plant Cell, 2:1261-1272; Munroe et al., (1990), Gene, 91:151-158; Ballas et al., (1989), Nucleic Acids Res., 17:7891-7903; Joshi et al., (1987), Nucleic Acid Res., 15:9627-9639.
For tissue specific expression, the nucleotide sequences of the invention can be operably linked to tissue specific promoters. See, for example, U.S. application Ser. No. 07/951,715 herein incorporated by reference.
It is recognized that the genes encoding the pesticidal proteins can be used to transform insect pathogenic organisms. Such organisms include Baculoviruses, fungi, protozoa, bacteria and nematodes.
The Bacillus strains of the invention may be used for protecting agricultural crops and products from pests. Alternatively, a gene encoding the pesticide may be introduced via a suitable vector into a microbial host, and said host applied to the environment or plants or animals. Microorganism hosts may be selected which are known to occupy the "phytosphere" (phylloplane, phyllosphere, rhizosphere, and/or rhizoplana) of one or more crops of interest. These microorganisms are selected so as to be capable of successfully competing in the particular environment with the wild-type microorganisms, provide for stable maintenance and expression of the gene expressing the polypeptide pesticide, and, desirably, provide for improved protection of the pesticide from environmental degradation and inactivation.
Such microorganisms include bacteria, algae, and fungi. Of particular interest are microorganisms, such as bacteria, e.g., Pseudomonas, Erwinia, Serratia, Klebsiella, Xanthomonas, Streptomyces, Rhizobium, Rhodopseudomonas, Methylius, Agrobacterium, Acetobacter, Lactobacillus, Arthrobacter, Azotobacter, Leuconostoc, and Alcaligenes; fungi particularly yeast, e.g., Saccharomyces, Cryptococcus, Kluyveromyces, Sporobolomyces, Rhodotorula, and Aureobasidium. Of particular interest are such phytosphere bacterial species as Pseudomonas syringae, Pseudomonas fluorescens, Serratia marcescens, Acetobacter xylinum, Agrobacteria, Rhodopseudomonas spheroides, Xanthomonas campestris, Rhizobium melioti, Alcaligenes entrophus, Clavibacter xyli and Azotobacter vinlandii; and phytosphere yeast species such as Rhodotorula rubra, R. glutinis, R. marina, R. aurantiaca, Cryptococcus albidus, C. diffluens, C. laurentii, Saccharomyces rosei, S. pretoriensis, S. cerevisiae, Sporobolomyces rosues, S. odorus, Kluyveromyces veronae, and Aureobasidium pollulans. Of particular interest are the pigmented microorganisms.
A number of ways are available for introducing a gene expressing the pesticidal protein into the microorganism host under conditions which allow for stable maintenance and expression of the gene. For example, expression cassettes can be constructed which include the DNA constructs of interest operably linked with the transcriptional and translational regulatory signals for expression of the DNA constructs, and a DNA sequence homologous with a sequence in the host organism, whereby integration will occur, and/or a replication system which is functional in the host, whereby integration or stable maintenance will occur.
Transcriptional and translational regulatory signals include but are not limited to promoter, transcriptional initiation start site, operators, activators, enhancers, other regulatory elements, ribosomal binding sites, an initiation codon, termination signals, and the like. See, for example, U.S. Pat. No. 5,039,523; U.S. Pat. No. 4,853,331; EPO 0480762A2; Sambrook et al. supra; Molecular Cloning, a Laboratory Manual, Maniatis et al. (eds) Cold Spring Harbor Laboratory, Cold Spring Harbor, N.Y. (1982); Advanced Bacterial Genetics, Davis et al. (eds.) Cold Spring Harbor Laboratory, Cold Spring Harbor, N.Y. (1980); and the references cited therein.
Suitable host cells, where the pesticide-containing cells will be treated to prolong the activity of the toxin in the cell when the then treated cell is applied to the environment of the target pest(s), may include either prokaryotes or eukaryotes, normally being limited to those cells which do not produce substances toxic to higher organisms, such as mammals. However, organisms which produce substances toxic to higher organisms could be used, where the toxin is unstable or the level of application sufficiently low as to avoid any possibility of toxicity to a mammalian host. As hosts, of particular interest will be the prokaryotes and the lower eukaryotes, such as fungi. Illustrative prokaryotes, both Gram-negative and -positive, include Enterobacteriaceae, such as Escherichia, Erwinia, Shigella, Salmonella, and Proteus; Bacillaceae; Rhizobiceae, such as Rhizobium; Spirillaceae, such as photobacterium, Zymomonas, Serratia, Aeromonas, Vibrio, Desulfovibrio, Spirillum; Lactobacillaceae; Pseudomonadaceae, such as Pseudomonas and Acetobacter; Azotobacteraceae and Nitrobacteraceae. Among eukaryotes are fungi, such as Phycomycetes and Ascomycetes, which includes yeast, such a Saccharomyces and Schizosaccharromyces; and Basidiomycetes yeast, such as Rhodotorula, Aureobasidium, Sporobolomyces, and the like.
Characteristics of particular interest in selecting a host cell for purposes of production include ease of introducing the protein gene into the host, availability of expression systems, efficiency of expression, stability of the protein in the host, and the presence of auxiliary genetic capabilities. Characteristics of interest for use as a pesticide microcapsule include protective qualities for the pesticide, such as thick cell walls, pigmentation, and intracellular packaging or formation of inclusion bodies; leaf affinity; lack of mammalian toxicity; attractiveness to pests for ingestion; ease of killing and fixing without damage to the toxin; and the like. Other considerations include ease of formulation and handling, economics, storage stability, and the like.
Host organisms of particular interest include yeast, such as Rhodotorula sp., Aureobasidium sp., Saccharomyces sp., and Sporobolomyces sp.; phylloplane organisms such as Pseudomonas sp., Erwinia sp. and Flavobacterium sp.; or such other organisms as Escherichia, LactoBacillus sp., Bacillus sp., and the like. Specific organisms include Pseudomonas aeurginosa, Pseudomonasfluorescens, Saccharomyces cerevisiae, Bacillus thuringiensis, Escherichia coli, Bacillus subtilis, and the like.
VIP genes can be introduced into micro-organisms that multiply on plants (epiphytes) to deliver VIP proteins to potential target pests. Epiphytes can be gram-positive or gram-negative bacteria for example.
Root colonizing bacteria, for example, can be isolated from the plant of interest by methods known in the art. Specifically, a Bacillus cereus strain which colonizes roots could be isolated from roots of a plant (for example see J. Handelsman, S. Raffel, E. Mester, L. Wunderlich and C. Grau, Appl. Environ. Microbiol. 56:713-718, (1990)). VIP1 and/or VIP2 could be introduced into a root colonizing Bacillus cereus by standard methods known in the art.
Specifically, VIP1 and/or VIP2 derived from Bacillus cereus strain AB78 can be introduced into a root colonizing Bacillus cereus by means of conjugation using standard methods (J. Gonzalez, B. Brown and B. Carlton, Proc. Natl. Acad. Sci. 79:6951-6955, (1982)).
Also, VIP1 and/or VIP2 or other VIPs of the invention can be introduced into the root colonizing Bacillus by means of electro-transformation. Specifically, VIPs can be cloned into a shuttle vector, for example, pHT3101 (D. Lereclus et al., FEMS Microbiol. Letts., 60:211-218 (1989)) as described in Example 10. The shuttle vector pHT3101 containing the coding sequence for the particular VIP can then be transformed into the root colonizing Bacillus by means of electroporation (D. Lereclus et al. 1989, FEMS Microbiol. Letts. 60:211-218).
Expression systems can be designed so that VIP proteins are secreted outside the cytoplasm of gram negative bacteria, E. coli, for example. Advantages of having VIP proteins secreted are (1) it avoids potential toxic effects of VIP proteins expressed within the cytoplasm and (2) it can increase the level of VIP protein expressed and (3) can aid in efficient purification of VIP protein.
VIP proteins can be made to be secreted in E. coli, for example, by fusing an appropriate E. coli signal peptide to the amino-terminal end of the VIP signal peptide or replacing the VIP signal peptide with the E. coli signal peptide. Signal peptides recognized by E. coli can be found in proteins already known to be secreted in E. coli, for example the OmpA protein (J. Ghrayeb, H. Kimura, M. Takahara, Y. Masui and M. Inouye, EMBO J., 3:2437-2442 (1984)). OmpA is a major protein of the E. coli outer membrane and thus its signal peptide is thought to be efficient in the translocation process. Also, the OmpA signal peptide does not need to be modified before processing as may be the case for other signal peptides, for example lipoprotein signal peptide (G. Duffaud, P. March and M. Inouye, Methods in Enzymology. 153:492 (1987)).
Specifically, unique BamHI restriction sites can be introduced at the amino-terminal and carboxy-terminal ends of the VIP coding sequences using standard methods known in the art. These BamHI fragments can be cloned, in frame, into the vector pIN-III-ompA1, A2 or A3 (J. Ghrayeb, H. Kimura, M. Takahara, H. Hsiung, Y. Masui and M. Inouye, EMBO J., 3:2437-2442 (1984)) thereby creating ompA:VIP fusion gene which is secreted into the periplasmic space. The other restriction sites in the polylinker of pIN-III-ompA can be eliminated by standard methods known in the art so that the VIP amino-terminal amino acid coding sequence is directly after the ompA signal peptide cleavage site. Thus, the secreted VIP sequence in E. coli would then be identical to the native VIP sequence.
When the VIP native signal peptide is not needed for proper folding of the mature protein, such signal sequences can be removed and replaced with the ompA signal sequence. Unique BamHI restriction sites can be introduced at the amino-termini of the proprotein coding sequences directly after the signal peptide coding sequences of VIP and at the carboxy-termini of VIP coding sequence. These BamHI fragments can then be cloned into the pIN-III-ompA vectors as described above.
General methods for employing the strains of the invention in pesticide control or in engineering other organisms as pesticidal agents are known in the art. See, for example U.S. Pat. No. 5,039,523 and EP 0480762A2.
VIPs can be fermented in a bacterial host and the resulting bacteria processed and used as a microbial spray in the same manner that Bacillus thuringiensis strains have been used as insecticidal sprays. In the case of a VIP(s) which is secreted from Bacillus, the secretion signal is removed or mutated using procedures known in the art. Such mutations and/or deletions prevent secretion of the VIP protein(s) into the growth medium during the fermentation process. The VIPs are retained within the cell and the cells are then processed to yield the encapsulated VIPs. Any suitable microorganism can be used for this purpose. Psuedomonas has been used to express Bacillus thuringiensis endotoxins as encapsulated proteins and the resulting cells processed and sprayed as an insecticide. (H. Gaertner et al. 1993, In Advanced Engineered Pesticides, L. Kim ed.)
Various strains of Bacillus thuringiensis are used in this manner. Such Bt strains produce endotoxin protein(s) as well as VIPs. Alternatively, such strains can produce only VIPs. A sporulation deficient strain of Bacillus subtilis has been shown to produce high levels of the CryIIIA endotoxin from Bacillus thuringiensis (Agaisse, H. and Lereclus, D., "Expression in Bacillus subtilis of the Bacillus thuringiensis CryIIIA toxin gene is not dependent on a sporulation-specific sigma factor and is increased in a spoOA mutant", J. Bacteriol. 176:4734-4741 (1994)). A similar spoOA mutant can be prepared in Bacillus thuringiensis and used to produce encapsulated VIPs which are not secreted into the medium but are retained within the cell.
To have VIPs maintained within the Bacillus cell the signal peptide can be disarmed so that it no longer functions as a secretion signal. Specifically, the putative signal peptide for VIP1 encompasses the first 31 amino acids of the protein with the putative consensus cleavage site, Ala-X-Ala, at the C-terminal portion of this sequence (G. von Heijne, J. Mol. Biol. 184:99-105 (1989)) and the putative signal peptide for VIP2 encompasses the first 40 amino acids of the protein with the putative cleavage site after Ala40. The cleavage sites in either VIP1 or VIP2 can be mutated with methods known in the art to replace the cleavage site consensus sequence with alternative amino acids that are not recognized by the signal peptidases.
Alternatively, the signal peptides of VIP 1, VIP2 and/or other VIPs of the invention can be eliminated from the sequence thereby making them unrecognizable as secretion proteins in Bacillus. Specifically, a methionine start site can be engineered in front of the proprotein sequence in VIP1, starting at Asp32, or the proprotein sequence in VIP2, starting at Glu41 using methods known in the art.
VIP genes can be introduced into micro-organisms that multiply on plants (epiphytes) to deliver VIP proteins to potential target pests. Epiphytes can be gram-positive or gram-negative bacteria for example.
The Bacillus strains of the invention or the microorganisms which have been genetically altered to contain the pesticidal gene and protein may be used for protecting agricultural crops and products from pests. In one aspect of the invention, whole, i.e., unlysed, cells of a toxin (pesticide)-producing organism are treated with reagents that prolong the activity of the toxin produced in the cell when the cell is applied to the environment of target pest(s).
Alternatively, the pesticides are produced by introducing a heterologous gene into a cellular host. Expression of the heterologous gene results, directly or indirectly, in the intracellular production and maintenance of the pesticide. These cells are then treated under conditions that prolong the activity of the toxin produced in the cell when the cell is applied to the environment of target pest(s). The resulting product retains the toxicity of the toxin. These naturally encapsulated pesticides may then be formulated in accordance with conventional techniques for application to the environment hosting a target pest, e.g., soil, water, and foliage of plants. See, for example EPA 0192319, and the references cited therein.
The active ingredients of the present invention are normally applied in the form of compositions and can be applied to the crop area or plant to be treated, simultaneously or in succession, with other compounds. These compounds can be both fertilizers or micronutrient donors or other preparations that influence plant growth. They can also be selective herbicides, insecticides, fungicides, bactericides, nematicides, mollusicides or mixtures of several of these preparations, if desired, together with further agriculturally acceptable carriers, surfactants or application-promoting adjuvants customarily employed in the art of formulation. Suitable carriers and adjuvants can be solid or liquid and correspond to the substances ordinarily employed in formulation technology, e.g. natural or regenerated mineral substances, solvents, dispersants, wetting agents, tackifiers, binders or fertilizers.
Preferred methods of applying an active ingredient of the present invention or an agrochemical composition of the present invention which contains at least one of the pesticidal proteins produced by the bacterial strains of the present invention are leaf application, seed coating and soil application. The number of applications and the rate of application depend on the intensity of infestation by the corresponding pest.
In one embodiment of the invention a Bacillus cereus microorganism has been isolated which is capable of killing Diabrotica virgifera virgifera, and Diabrotica longicornis barberi. The novel B. cereus strain AB78 has been deposited in the Agricultural Research Service, Patent Culture Collection (NRRL), Northern Regional Research Center, 1815 North University Street, Peoria, Ill. 61604, USA and given Accession No. NRRL B-21058.
A fraction protein has been substantially purified from the B. cereus strain. This purification of the protein has been verified by SDS-PAGE and biological activity. The protein has a molecular weight of about 60 to about 100 kDa, particularly about 70 to about 90 kDa, more particularly about 80 kDa, hereinafter VIP.
Amino-terminal sequencing has revealed the N-terminal amino-acid sequence to be: NH.sub.2 -Lys-Arg-Glu-Ile-Asp-Glu-Asp-Thr-Asp-Thr-Asx-Gly-Asp-Ser-Ile-Pro-(SEQ ID NO:8) where Asx represents either Asp or Asn. The entire amino acid sequence is given in SEQ ID NO:7. The DNA sequence which encodes the amino acid sequence of SEQ ID NO:7 is disclosed in SEQ ID NO:6.
An oligonucleotide probe for the region of the gene encoding amino acids 3-9 of the NH.sub.2 -terminus has been generated. The probe was synthesized based on the codon usage of a Bacillus thuringiensis (Bt) .delta.-endotoxin gene. The nucleotide sequence of the oligonucleotide probe used for Southern hybridizations was as follows:
5'-GAA ATT GAT CAA GAT ACN GAT-3' (SEQ ID NO:9)
where N represents any base.
In addition, the DNA probe for the Bc AB78 VIP1 gene described herein, permits the screening of any Bacillus strain or other organisms to determine whether the VIP 1 gene (or related gene) is naturally present or whether a particular transformed organism includes the VIP1 gene.
The invention now being generally described, the same will be better understood by reference to the following detailed examples that are provided for the purpose of illustration and are not to be considered limiting of the invention unless so specified.
A standard nomenclature has been developed based on the sequence identity of the proteins encompassed by the present invention. The gene and protein names for the detailed examples which follow and their relationship to the names used in the parent application are shown below.
Experimental
EXAMPLE 1
AB78 Isolation and Characterization
Bacillus cereus strain AB78 was isolated as a plate contaminant in the laboratory on T3 media (per liter: 3 g tryptone, 2 g tryptose, 1.5 g yeast extract, 0.05M sodium phosphate (pH 6.8), and 0.005 g MnCl.sub.2 ; Travers, R. S. 1983). During log phase growth, AB78 gave significant activity against western corn rootworm. Antibiotic activity against gram-positive Bacillus spp. was also demonstrated (Table 12).
Morphological characteristics of AB78 are as follows: Vegetative rods straight, 3.1-5.0 mm long and 0.5-2.0 mm wide. Cells with rounded ends, single in short chains. Single subterminal, cylindrical-oval, endospore formed per cell. No parasporal crystal formed. Colonies opaque, erose, lobate and flat. No pigments produced. Cells motile. Flagella present.
Growth characteristics of AB78 are as follows:
Facultative anaerobe with optimum growth temperature of 21.degree.-30.degree. C. Will grow at 15.degree., 20.degree., 25.degree., 30.degree. and 37.degree. C. Will not grow above 40.degree. C. Grows in 5-7% NaCl.
Table 13 provides the biochemical profile of AB78.
EXAMPLE 2
Bacterial Culture
A subculture of Bc strain AB78 was used to inoculate the following medium, known as TB broth:
The potassium phosphate was added to the autoclaved broth after cooling. Flasks were incubated at 30.degree. C. on a rotary shaker at 250 rpm for 24 h.-36 h, which represents an early to mid-log growth phase.
The above procedure can be readily scaled up to large fermentors by procedures well known in the art.
During vegetative growth, usually 24-36 h. after starting the culture, which represents an early to mid-log growth phase, AB78 bacteria were centrifuged from the culture supernatant. The culture supernatant containing the active protein was used in bioassays.
EXAMPLE 3
Insect Bioassays
B. cereus strain AB78 was tested against various insects as described below.
Western, Northern and Southern corn rootworm, Diabrotica virgifera virgifera, D. longcornis barberi and D. undecempunctata howardi, respectively: dilutions were made of AB78 culture supernatant grown 24-36 h., mixed with molten artificial diet (Marrone et al. (1985) J. of Economic Entomology 78:290-293) and allowed to solidify. Solidified diet was cut and placed in dishes. Neonate larvae were placed on the diet and held at 30.degree. C. Mortality was recorded after 6 days.
E. coli clone bioassay: E. coli cells were grown overnight in broth containing 100 .mu.g/ml ampicillin at 37.degree. C. Ten ml culture was sonicated 3.times. for 20 sec each. 500 .mu.l of sonicated culture was added to molten western corn rootworm diet.
Colorado potato beetle, Leptinotarsa decemlineata: dilutions in Triton X-100 (to give final concentration of 0.1% TX-100) were made of AB78 culture supernatant grown 24-36 h. Five cm.sup.2 potato leaf pieces were dipped into these dilutions, air dried, and placed on moistened filter paper in plastic dishes. Neonate larvae were placed on the leaf pieces and held at 30.degree. C. Mortality was recorded after 3-5 days.
Yellow mealworm, Tenebrio molitor: dilutions were made of AB78 culture supernatant grown 24-36 h., mixed with molten artificial diet (Bioserv #F9240) and allowed to solidify. Solidified diet was cut and placed in plastic dishes. Neonate larvae were placed on the diet and held at 30.degree. C. Mortality was recorded after 6-8 days.
European corn borer, black cutworm, tobacco budworm, tobacco hornworm and beet armyworm; Ostrinia nubilalis, Agrotis ipsilon, Heliothis virescens, Manduca sexta and Spodoptera exigua, respectively: dilutions, in TX-100 (to give final concentration of 0.1% TX-100), were made of AB78 culture supernatant grown 24-36 hrs. 100 .mu.l was pipetted onto the surface of 18 cm.sup.2 of solidified artificial diet (Bioserv #F9240) and allowed to air dry. Neonate larvae were then placed onto the surface of the diet and held at 30.degree. C. Mortality was recorded after 3-6 days.
Northern house mosquito, Culex pipiens:-dilutions were made of AB78 culture supernatant grown 24-36 h. 100 .mu.l was pipetted into 10 ml water in a 30 ml plastic cup. Third instar larvae were added to the water and held at room temperature. Mortality was recorded after 24-48 hours. The spectrum of entomocidal activity of AB78 is given in Table 14.
The newly discovered B. cereus strain AB78 showed a significantly different spectrum of insecticidal activity as compared to known coleopteran active .delta.-endotoxins from Bt. In particular, AB78 showed more selective activity against beetles than known coleopteran-active Bt strains in that it was specifically active against Diabrotica spp. More specifically, it was most active against D. virgifera virgifera and D. longicornis barberi but not D. undecimpunctata howardi.
A number of Bacillus strains were bioassayed for activity during vegetative growth (Table 15) against western corn rootworm. The results demonstrate that AB78 is unique in that activity against western corn rootworm is not a general phenomenon.
Specific activity of AB78 against western corn rootworm is provided in Table 16.
The LC.sub.50 was calculated to be 6.2 .mu.l of culture supernatant per ml of western corn rootworm diet.
The cell pellet was also bioassayed and had no activity against WCRW. Thus, the presence of activity only in the supernatant indicates that this VIP is an exotoxin.
EXAMPLE 4
Isolation and Purification of Corn Rootworm Active Proteins from AB78.
Culture media free of cells and debris was made to 70% saturation by the addition of solid ammonium sulfate (472 g/L). Dissolution was at room temperature followed by cooling in an ice bath and centrifugation at 10,000.times.g for thirty minutes to pellet the precipitated proteins. The supernatant was discarded and the pellet was dissolved in 1/10 the original volume of 20 mM TRIS-HCl at pH 7.5. The dissolved pellet was desalted either by dialysis in 20 mM TRIS-HCl pH 7.5, or passing through a desalting column.
The desalted material was titrated to pH 3.5 using 20 mM sodium citrate pH 2.5. Following a thirty minute room temperature incubation the solution was centrifuged at 3000.times.g for ten minutes. The supernatant at this stage contained the greatest amount of active protein.
Following neutralization of the pH to 7.0 the supernatant was applied to a Mono-Q, anion exchange, column equilibrated with 20 mM TRIS pH 7.5 at a flow rate of 300 mL/min. The column was developed with a stepwise and linear gradient employing 400 mM NaCl in 20 mM TRIS pH 7.5.
Bioassay of the column fractions and SDS-PAGE analysis were used to confirm the active fractions. SDS-PAGE analysis identified the biologically active protein as having components of a molecular weight in the range of about 80 kDa and 50 kDa.
EXAMPLE 5
Sequence Analysis of the Corn Rootworm Active Protein
The 80 kDa component isolated by SDS-PAGE was transferred to PVDF membrane and was subjected to amino-terminal sequencing as performed by repetitive Edman cycles on an ABI 470 pulsed-liquid sequencer. Transfer was carried out in 10 mM CAPS buffer with 10% methanol pH 11.0 as follows:
Incubation of the gel following electrophoresis was done in transfer buffer for five minutes. ProBlott PVDF membrane was wetted with 100% MeOH briefly then equilibrated in transfer buffer. The sandwich was arranged between foam sponges and filter paper squares with the configuration of cathode-gel-membrane-anode.
Transfer was performed at 70 V constant voltage for 1 hour.
Following transfer, the membrane was rinsed with water and stained for two minutes with 0.25% Coomassie Blue R-250 in 50% MeOH.
Destaining was done with several rinses with 50% MeOH 40% water 10% acetic acid.
Following destaining the membrane was air dried prior to excision of the bands for sequence analysis. A BlottCartridge and appropriate cycles were utilized to achieve maximum efficiency and yield. Data analysis was performed using model 610 Sequence Analysis software for identifying and quantifying the PTH-amino acid derivatives for each sequential cycle.
The N-terminal sequence was determined to be: NH2-Lys-Arg-Glu-Ile-Asp-Glu-Asp-Thr-Asp-Thr-Asx-Gly-Asp-Ser-Ile-Pro-(SEQ ID NO:8) where Asx represents Asp or Asn. The complete amino acid sequence for the 80 kDa component is disclosed in SEQ ID NO:7. The DNA sequence which encodes SEQ ID NO:7 is disclosed in SEQ ID NO:6.
EXAMPLE 6
Construction of DNA Probe
An oligonucleotide probe for the region of the gene encoding amino acids 3-9 of the N-terminal sequence (Example 5) was generated. The probe was synthesized based on the codon usage of a Bacillus thuringiensis (Bt) .delta.-endotoxin gene. The nucleotide sequence
5'-GAA ATT GAT CAA GAT ACN GAT-3' (SEQ ID NO:9)
was used as a probe in Southern hybridizations. The oligonucleotide was synthesized using standard procedures and equipment.
EXAMPLE 7
Isoelectric Point Determination of the Corn Rootworm Active Protein
Purified protein from step 5 of the purification process was analyzed on a 3-9 pI isoelectric focusing gel using the Phastgel electrophoresis system (Pharmacia). Standard operating procedures for the unit were followed for both the separation and silver staining development procedures. The pI was approximated at about 4.9.
EXAMPLE 8
PCR Data on AB78
PCR analysis (See, for example U.S. patent application Ser. No. 08/008,006; and, Carozzi et al. (1991) Appl. Environ. Microbiol. 57(11):3057-3061, herein incorporated by reference.) was used to verify that the B. cereus strain AB78 did not contain any insecticidal crystal protein genes of B. thuringiensis or B. sphaericus (Table 17).
EXAMPLE 9
Cosmid Cloning of Total DNA from B. Cereus Strain AB78
The VIP1A(a) gene was cloned from total DNA prepared from strain AB78 as follows:
Isolation of AB78 DNA was as follows:
1. Grow bacteria in 10 ml L-broth overnight. (Use 50 ml sterile centrifuge tube)
2. Add 25 ml of fresh L-broth and ampicillin (30 .mu.g/ml).
3. Grow cells 2-6 h. at 30.degree. C. with shaking;
4. Spin cells in a 50 ml polypropylene orange cap tube in IEC benchtop clinical centrifuge at 3/4 speed.
5. Resuspend cell pellet in 10 ml TES (TES=50 mM TRIS pH 8.0, 100 mM EDTA, 15 mM NaCl).
6. Add 30 mg lysozyme and incubate 2 hrs at 37.degree. C.
7. Add 200 .mu.l 20% SDS and 400 .mu.l Proteinase K stock (20 mg/ml). Incubate at 37.degree. C.
8. Add 200 .mu.l fresh Proteinase K. Incubate 1 hr. at 55.degree. C. Add 5 ml TES to make 15 ml final volume.
9. Phenol extract twice (10 ml phenol, spin at room temperature at 3/4 speed in an IEC benchtop clinical centrifuge). Transfer supernatant (upper phase) to a clean tube using a wide bore pipette.
10. Extract once with 1:1 vol. phenol:chloroform/isoamyl alcohol (24:1 ratio).
11. Precipitate DNA with an equal volume of cold isopropanol; Centrifuge to pellet DNA.
12. Resuspend pellet in 5 ml TE.
13. Precipitate DNA with 0.5 ml 3M NaOAc pH 5.2 and 11 ml 95% ethanol. Place at -20.degree. C. for 2 h.
14. "Hook" DNA from tube with a plastic loop, transfer to a microfuge tube, spin, pipette off excess ethanol, dry in vacuo.
15. Resuspend in 0.5 ml TE. Incubate 90 min. at 65.degree. C. to help get DNA back into solution.
16. Determine concentration using standard procedures.
Cosmid Cloning of AB78
All procedures, unless indicated otherwise, were performed according to Stratagene Protocol, Supercos 1 Instruction Manual, Cat. No. 251301.
Generally, the steps were as follows:
A. Sau 3A partial digestion of the AB78 DNA.
B. Preparation of vector DNA
C. Ligation and packaging of DNA
D. Tittering the cosmid library
1. Start a culture of HB101 cells by placing 50 ml of an overnight culture in 5 mls of TB with 0.2% maltose. Incubate 3.5 hrs. at 37.degree. C.
2. Spin out cells and resuspend in 0.5 ml 10 mM MgSO.sub.4.
3. Add together: 100 .mu.l cells 100 .mu.l diluted packaging mixture 100 .mu.l 10 mM MgSO.sub.4 30 .mu.l TB
4. Adsorb at room temperature for 30 minutes with no shaking.
5. Add 1 ml TB and mix gently. Incubate 30 minutes at 37.degree. C.
6. Plate 200 .mu.l onto L-amp plates. Incubate at 37.degree. C overnight.
At least 400 cosmid clones were selected at random and screened for activity against western corn rootworm as described in Example 3. DNA from 5 active clones and 5 non-active clones were used in Southern hybridizations. Results demonstrated that hybridization using the above described oligonucleotide probe correlated with western corn rootworm activity (Table 18).
Cosmid clones P3-12 and P5-4 have been deposited with the Agricultural Research Service Patent Culture Collection (NRRL) and given Accession Nos. NRRL B-21061 and NRRL B-21059 respectively.
EXAMPLE 10
Identification of a 6 KB Region Active against Western Corn Rootworm
DNA from P3-12 was partially digested with restriction enzyme Sau 3A, and ligated into the E. coli vector pUC 19 and transformed into E. coli. A DNA probe specific for the 80 kDa VIP1A(a) protein was synthesized by PCR amplification of a portion of P3-12 DNA. Oligonucleotides MK113 and MK117, which hybridize to portions of VIP1A(a), were synthesized using the partial amino acid sequence of the 80 kDa protein. Plasmid subclones were identified by colony hybridization to the PCR-generated probe, and tested for activity against western corn rootworm. One such clone, PL2, hybridized to the PCR-generated fragment, and was active against western corn rootworm in the assay previously described.
A 6 kb Cla I restriction fragment from pL2 was cloned into the Sma I site of the E. coli-Bacillus shuttle vector pHT 3101 (Lereclus, D. et al., FEMS Microbiology Letters 60:211-218 (1989)) to yield pCIB6201. This construct confers anti-western corn rootworm activity upon both Bacillus and E.coli strains, in either orientation. pCIB6022 contains this same 6 kb Cla I fragment in pBluescript SK(+) (Stratagene), produces equivalent VIP1A(a) protein (by western blot), and is also active against western corn rootworm.
The nucleotide sequence of pCIB6022 was determined by the dideoxy termination method of Sanger et al., Proc. Natl. Acad. Sci. USA, 74:5463-5467 (1977), using PRISM Ready Reaction Dye Deoxy Terminator Cycle Sequencing Kits and PRISM Sequenase.RTM. Terminator Double-Stranded DNA Sequencing Kit and analyzed on an ABI 373 automatic sequencer. The sequence is given in SEQ ID NO:1. The 6 kb fragment encodes both VIP1A(a) and VIP2A(a), as indicated by the open reading frames described in SEQ ID NO:1. The sequence encoding VIP1A(a) is further disclosed in SEQ ID NO:4. The relationship between VIP1A(a) and VIP2A(a) within the 6 kb fragment found in pCIB6022 is depicted in FIG. 1. pCIB6022 was deposited with the Agricultural Research Service, Patent Culture Collection, (NRRL), Northern Regional Research Center, 1815 North University Street, Peoria, Ill. 61604, USA, and given the Accession No. NRRL B-21222.
EXAMPLE 11
Functional Dissection of the VIP1A(a) DNA REGION
To confirm that the VIP1A(a) open reading frame (ORF) is necessary for insecticidal activity a translational frameshift mutation was created in the gene. The restriction enzyme Bg1 II recognizes a unique site located 857 bp into the coding region of VIP1A(a). pCIB6201 was digested with Bg1 II, and the single-stranded ends filled-in with DNA polymerase (Klenow fragment) and dNTPS. The plasmid was re-ligated and transformed into E. coli. The resulting plasmid, pCIB6203, contains a four nucleotide insertion in the coding region of VIP1A(a). pCIB6203 does not confer WCRW insecticidal activity, confirming that VIP1A(a) is an essential component of western corn rootworm activity.
To further define the region necessary to encode VIP1A(a), subclones of the VIP1A(a) and VIP2A(a) (auxiliary protein) region were constructed and tested for their ability to complement the mutation in pCIB6203. pCIB6023 contains the 3.7 kb Xba I-EcoRV fragment in pBluescript SK(+) (Stratagene). Western blot analysis indicates that pCIB6023 produces VIP1A(a) protein of equal size and quantity as clones PL2 and pCIB6022. pCIB6023 contains the entire gene encoding the 80 kD protein. pCIB6023 was deposited with the Agricultural Research Service, Patent Culture Collection, (NRRL), Northern Regional Research Center, 1815 North University Street, Peoria, Ill. 61604, USA, and given the Accession No. NRRL B-21223N. pCIB6206 contains the 4.3 kb Xba I-Cla I fragment from pCIB6022 in pBluescript SK(+) (Stratagene). pCIB6206 was also deposited with the Agricultural Research Service, Patent Culture Collection, (NRRL), Northern Regional Research Center, 1815 North University Street, Peoria, Ill. 61604, USA, and given the Accession No. NRRL B-21321.
pCIB6023, pCIB6206, and pCIB6203 do not produce detectable western corn rootworm activity when tested individually. However, a mixture of cells containing pCIB6203 (VIP1A(a)-mutated, plus VIP2A(a)) and cells containing pCIB6023 (only VIP1A(a)) shows high activity against western corn rootworm. Similarly, a mixture of cells containing pCIB6206 and cells containing pCIB6203 shows high activity against western corn rootworm.
To further define the limits of VIP2A(a), we constructed pCIB6024, which contains the entirety of VIP2A(a), but lacks most of the VIP1A(a) coding region. pCIB6024 was constructed by gel purifying the 2.2 kb Cla I-Sca I restriction fragment from pCIB6022, filling in the single-stranded ends with DNA polymerase (Klenow fragment) and dNTPs, and ligating this fragment into pBluescript SK(+) vector (Stratagene) digested with the enzyme Eco RV. Cells containing pCIB6024 exhibit no activity against western corn rootworm. However, a mixture of cells containing pCIB6024 and cells containing pCIB6023 shows high activity against western corn rootworm. (See FIG. 1).
Thus, pCIB6023 and pCIB6206 must produce a functional VIP1A(a) gene product, while pCIB6203 and pCIB6024 must produce a functional VIP2A(a) gene product. These results suggest a requirement for a gene product(s) from the VIP2A(a) regions in combination with VIP1A(a), to confer maximal western corn rootworm activity. (See FIG. 1)
EXAMPLE 12
AB78 Antibody Production
Antibody production was initiated in 2 Lewis rats to allow for both the possibility of moving to production of hybridoma cell lines and also to produce enough serum for limited screening of genomic DNA library. Another factor was the very limited amount of antigen available and the fact that it could only be produced to purity by PAGE and subsequent electrotransfer to nitrocellulose.
Due to the limited availability of antigen on nitrocellulose, the nitrocellulose was emulsified in DMSO and injected into the hind footpads of the animals to elicit B-cell production in the popliteal lymph nodes just upstream. A strong reacting serum was produced as judged by western blot analysis with the first production bleed. Several subsequent injections and bleeds produced enough serum to accomplish all of the screening required.
Hybridoma production with one of the rats was then initiated. The popliteal lymph node was excised, macerated, and the resulting cells fused with mouse myeloma P3x63Ag8.653. Subsequent cell screening was accomplished as described below. Four initial wells were selected which gave the highest emulsified antigen reaction to be moved to limited dilution cloning. An additional 10 wells were chosen for expansion and cryoperservation.
Procedure to Emulsify AB78 on nitrocellulose in DMSO for ELISA screening:
After electrotransfer of AB78 samples run on PAGE to nitrocellulose, the reversible strain Ponceau S is used to visualize all protein transferred. The band corresponding to AB78 toxin, previously identified and N-terminal sequenced, was identified and excised from nitrocellulose. Each band is approximately 1 mm.times.5 mm in size to minimize the amount of nitrocellulose emulsified. A single band is placed in a microfuge tube with 250 .mu.l of DMSO and macerated using a plastic pestle (Kontes, Vineland, N.J.). To aid in emulsification, the DMSO mixture is heated for 2-3 minutes at 37.degree. C.-45.degree. C. Some further maceration might be necessary following heating; however, all of the nitrocellulose should be emulsified. Once the AB78 sample is emulsified, it is placed on ice. In preparation for microtiter plate coating with the emulsified antigen, the sample must be diluted in borate buffered saline as follows: 1:5, 1:10, 1:15, 1:20, 1:30, 1:50, 1:100, and 0. The coating antigen must be prepared fresh immediately prior to use.
ELISA protocol:
1. Coat with AB78/DMSO in BBS. Incubate overnight at 4.degree. C.
2. Wash plate 3.times. with 1.times.ELISA wash buffer.
3. Block (1% BSA & 0.05% Tween 20 in PBS) for 30 minutes at Room Temperature.
4. Wash plate 3.times. with 1.times.ELISA wash buffer.
5. Add rat serum. Incubate 1.5 hours at 37.degree. C.
6. Wash plate 3.times. with 1.times.ELISA wash buffer.
7. Add goat anti-rat at a concentration of 2 .mu.g/ml in ELISA diluent. Incubate 1 hr. at 37.degree. C.
8. Wash plate 3.times. with 1.times.ELISA wash buffer.
9. Add rabbit anti-goat alkaline phosphatase at 2 .mu.g/ml in ELISA diluent. Incubate 1 hr. at 37.degree. C.
10. Wash 3.times. with 1.times.ELISA wash buffer.
11. Add Substrate. Incubate 30 minutes at room temperature.
12. Stop with 3N NaOH after 30 minutes.
Preparation of VIP2A(a) Antisera
A partially purified AB78 culture supernatant was separated by discontinuous SDS PAGE (Novex) following manufacturer's instructions. Separated proteins were electrophoresed to nitrocellulose (S&S #21640) as described by Towbin et al., (1979). The nitrocellulose was stained with Ponceau S and the VIP2A(a) band identified. The VIP2A(a) band was excised and emulsified in DMSO immediately prior to injection. A rabbit was initially immunized with emulsified VIP2A(a) mixed approximately 1:1 with Freund's Complete adjuvant by intramuscular injection at four different sites. Subsequent immunizations occurred at four week intervals and were identical to the first, except for the use of Freund' Incomplete adjuvant. The first serum harvested following immunization reacted with VIP2A(a) protein. Western blot analysis of AB78 culture supernatant using this antisera identifies predominately full length VIP2A(a) protein.
EXAMPLE 13
Activation of Insecticidal Activity of Non-Active BT Strains with AB78 VIP Clones
Adding pCIB6203 together with a 24 h culture (early to mid-log phase) supernatant from Bt strain GC91 produces 100% mortality in Diabrotica virgifera virgifera. Neither pCIB6203 nor GC91 is active on Diabrotica virgifera virgifera by itself. Data are shown below:
EXAMPLE 14
Isolation and Biological Activity of B. cereus AB81
A second B. cereus strain, designated AB81, was isolated from grain bin dust samples by standard methodologies. A subculture of AB81 was grown and prepared for bioassay as described in Example 2. Biological activity was evaluated as described in Example 3. The results are as follows:
EXAMPLE 15
Isolation and Biological Activity of B. thuringiensis AB6
A B. thuringiensis strain, designated AB6, was isolated from grain bin dust samples by standard methods known in the art. A subculture of AB6 was grown and prepared for bioassay as described in Example 2. Half of the sample was autoclaved 15 minutes to test for the presence of .beta.-exotoxin.
Biological activity was evaluated as described in Example 3. The results are as follows:
The reduction of insecticidal activity of the culture supernatant to insignificant levels by autoclaving indicates that the active principle is not .beta.-exotoxin.
Strain AB6 has been deposited in the Agricultural Research Service, Patent Culture Collection (NRRL), Northern Regional Research Center, 1815 North University Street, Peoria, Ill. 61604, USA, and given Accession No. NRRL B-21060.
EXAMPLE 16
Isolation and Biological Characterization of B. Thuringiensis AB88
A Bt strain, designated AB88, was isolated from grain bin dust samples by standard methodologies. A subculture of AB88 was grown and prepared for bioassay as described in Example 2. Half of the sample was autoclaved 15 minutes to test for the presence of .beta.-exotoxin. Biological activity was evaluated against a number of insect species as described in Example 3. The results are as follows:
The reduction of insecticidal activity of the culture supernatant to insignificant levels by autoclaving indicates that the active principle is not .beta.-exotoxin.
Delta-endotoxin crystals were purified from strain AB88 by standard methodologies. No activity from pure crystals was observed when bioassayed against Agrotis ipsilon.
EXAMPLE 17
Purification of VIPS from strain AB88
Bacterial liquid culture was grown overnight at 30.degree. C. in TB media. Cells were spun out and the supernatant retained. Proteins were precipitated with ammonium sulfate (70% saturation), centrifuged and the pellet retained. The pellet was resuspended in the original volume of 20 mM Tris pH 7.5 and dialyzed against the same buffer. AB88 dialysate was more turbid than comparable material from AB78. AB88 proteins have been separated by several different methods following clarification including isoelectric focusing (Rotofor, BioRad, Hercules, Calif.), precipitation at pH 4.5, ion-exchange chromatography, size exclusion chromatography and ultrafiltration.
European corn borer (ECB)-active protein remained in the pellet obtained by pH 4.5 precipitation of dialysate. When preparative IEF was done on the dialysate using pH 3-10 ampholytes, ECB insecticidal activity was found in all fractions with pH of 7 or greater. SDS-PAGE analysis of these fractions showed protein bands of MW .about.60 kDa and .about.80 kDa. The 60 kDa and 80 kDa bands were separated by anion exchange HPLC on a Poros-Q column (PerSeptive Biosystems, Cambridge, Mass.). N-terminal sequence was obtained from two fractions containing proteins of slightly differing MW, but both of approximately 60 kDa in size. The sequences obtained were similar to each other and to some .delta.-endotoxins.
anion exchange fraction 23 (smaller): xEPFVSAxxxQxxx (SEQ ID NO:10)
anion exchange fraction 28 (larger): xEYENVEPFVSAx (SEQ ID NO:11)
When the ECB-active pH 4.5 pellet was further separated by anion exchange on a Poros-Q column, activity was found only in fractions containing a major band of .about.60 kDa.
Black cutworm-active protein also remained in the pellet when AB88 dialysate was brought down to pH 4.5. In preparative IEF using pH 3-10 ampholytes, activity was not found in the ECB-active IEF fractions; instead, it was highest in a fraction of pH 4.5-5.0. Its major components have molecular weights of .about.35 and .about.80 kDa.
The pH 4.5 pellet was separated by anion exchange HPLC to yield fractions containing only the 35 kDa material and fractions containing both 35 kDa and 80 kDa bands.
EXAMPLE 18
Characterization of AB88 VIP
Fractions containing the various lepidopteran active vegetative proteins were generated as described in Example 17. Biological analysis of fractions demonstrated that different VIPs were responsible for the different lepidopteran species activity.
The Agrotis ipsilon activity is due to an 80 kDa and/or a 35 kDa protein, either delivered singly or in combination. These proteins are not related to any .delta.-endotoxins from Bt as evidenced by the lack of sequence homology of known Bt .delta.-endotoxin sequences. Also, these proteins are not found in the AB88 .delta.-endotoxin crystal. N-terminal sequences of the major .delta.-endotoxin proteins were compared with the N-terminal sequences of the 80 kDa and 35 kDa VIP and revealed no sequence homology. A summary of the results follows:
The Ostrinia nubilalis activity is due to a 60 kDa VIP and the Spodoptera frugperda activity is due to a VIP of unknown size.
Bacillus thuringiensis strain AB88 has been deposited in the Agricultural Research Service, Patent Culture Collection (NRRL), Northern Regional Research Center, 1815 North University Street, Peoria, Ill. 61604, USA and given the Accession No. NRRL B-21225.
EXAMPLE 18A
Isolation and Biological Activity of B. Thuringiensis AB424
A B. thuringiensis strain, designated AB424, was isolated from a moss covered pine cone sample by standard methods known in the art. A subculture of AB424 was grown and prepared for bioassay as described in Example 2.
Biological activity was evaluated as described in Example 3. The results are as follows:
Strain AB424 has been deposited in the Agricultural Research Service, Patent Culture Collection (NRRL), Northern Regional Research Center, 1815 North University Street, Peoria, Ill. 61604, USA, and given Accession No. NRRL B-21439.
EXAMPLE 18B
Cloning of the VIP3A(a) and VIP3A(b) Genes which Encode Proteins Active against Black Cutworm
DNA from isolates AB88 and AB424 was digested with the restriction enzymes XbaI and EcoRI respectively, ligated into pBluescript vector previously linearized with the same enzymes and dephosphorylated, and transformed into E. coli DH5.alpha. strain. Recombinant clones were blotted onto nitrocellulose filters which were subsequently probed with a 33-bases long oligonucleotide corresponding to the 11-N terminal amino acids of the 80 kDa protein active against Agrotis ipsilon (black cutworm). Four out of 400 recombinant clones were positive. Insect bioassays of the positive recombinants exhibited toxicity to black cutworm larvae comparable to that of AB88 or AB424 supernatants.
The nucleotide sequence of pCIB7104, a positive recombinant clone from AB88, and of pCIB7107, a positive recombinant clone from AB424, was determined by the dideoxy termination method of Sanger et al., Proc. Natl. Acad. Sci. USA, 74:5463-5467 (1977), using PRISM Ready Reaction Dye Deoxy Terminator Cycle Sequencing Kits and PRISM Sequenase.RTM. Terminator Double-Stranded DNA Sequencing Kit and analysed on an ABI 373 automatic sequencer.
The clone pCIB7104 contains the VIP3A(a) gene whose coding region is disclosed in SEQ ID NO:28 and the encoded protein sequence is disclosed in SEQ ID NO:29. A synthetic version of the coding region designed to be highly expressed in maize is given in SEQ ID NO:30. Any number of synthetic genes can be designed based on the amino acid sequence given in SEQ ID NO:29.
The clone pCIB7107 contains the VIP3A(b) gene whose coding region is disclosed in SEQ ID NO:31 and the encoded protein is disclosed in SEQ ID NO:32. Both pCIB7104 and pCIB7107 have been deposited with the Agricultural Research Service Patent Culture Collection (NRRL) and given Accession Nos. NRRL B-21422 and B-21423, respectively.
EXAMPLE 18C
Identification of Novel VIP3-like Genes by Hybridization
To identify Bacillus containing genes related to the VIP3A(a) from isolate AB88, a collection of Bacillus isolates was screened by hybridization. Cultures of 463 Bacillus strains were grown in microtiter wells until sporulation. A 96-pin colony stampel was used to transfer the cultures to 150 mm plates containing L-agar. Inoculated plates were kept at 30.degree. C. for 10 hours, then at 4.degree. C. overnight. Colonies were blotted onto nylon filters and probed with a 1.2 Kb HindIII VIP3A(a) derived fragment. Hybridization was performed overnight at 62.degree. C. using hybridization conditions of Maniatis et al. Molecular Cloning: A Laboratory Manual (1982). Filters were washed with 2.times.SSC/0.1% SDS at 62.degree. C. and exposed to X-ray film.
Of the 463 Bacillus strains screened, 60 contain VIP3-like genes that could detected by hybridization.
EXAMPLE 18D
Characterization of A B. thuringiensis Strain M2194 containing a Cryptic VIP3-like Gene
A B. thuringiensis strain, designated M2194, was shown to contain VIP3-like gene(s) by colony hybridization as described in Example 18C. The M2194 VIP3 like gene is considered cryptic since no expression can be detected throughout the bacterial growth phases either by immunoblot analysis using polyclonal antibodies raised against the VIP3A(a) protein isolated from AB88 or by bioassay as described in Example 3.
The M2194 VIP3-like gene was cloned into pKS by following the protocol described in Example 9, which created pCIB7108. E. coli containing pCIB7108 which comprises the M2194 VIP3 gene were active against black cutworm demonstrating that the gene encodes a functional protein with insecticidal activity. The plasmid pCIB7108 has been deposited with the Agricultural Research Service Patent Culture Collection (NRRL) and given Accession No. NRRL B-21438.
EXAMPLE 19
Isolation and Biological Activity of other Bacillus SP.
Other Bacillus species have been isolated which produce proteins with insecticidal activity during vegetative growth. These strains were isolated from environmental samples by standard methodologies. Isolates were prepared for bioassay and assayed as described in Examples 2 and 3 respectively. Isolates which produced insecticidal proteins during vegetative growth with activity against Agrotis ipsilon in the bioassay are tabulated below. No correlation was observed between the presence of a .delta.-endotoxin crystal and vegetative insecticidal protein production.
Isolates AB289, AB294 and AB359 have been deposited in the Agricultural Research Service, Patent Culture Collection (NRRL), Northern Regional Research Center, 1815 North University Street, Peoria Ill. 61604, USA and given the Accession Numbers NRRL B-21227, NRRL B-21229, and NRRL B-21226 respectively.
Bacillus isolates which produce insecticidal proteins during vegetative growth with activity against Diabrotica virgifera virgifera are tabulated below.
Isolates AB59 and AB256 have been deposited in the Agricultural Research Service, Patent Culture Collection (NRRL), Northern Regional Research Center, 1815 North University Street, Peoria, Ill. 61604, USA, and given the Accession Numbers NRRL B-21228 and NRRL B-21230, respectively.
EXAMPLE 20
Identification of Novel VIP1/VIP2 like Genes by Hybridization
To identify strains containing genes related to those found in the VIP1A(a)/VIP2A(a) region of AB78, a collection of Bacillus strains was screened by hybridization. Independent cultures of 463 Bacillus strains were grown in wells of 96 well microtiter dishes (five plates total) until the cultures sporulated. Of the strains tested, 288 were categorized as Bacillus thuringiensis, and 175 were categorized as other Bacillus species based on the presence or absence of .delta.-endotoxin crystals. For each microtiter dish, a 96-pin colony stamper was used to transfer approximately 10 .mu.l of spore culture to two 150 mm plates containing L-agar. Inoculated plates were grown 4-8 hours at 30.degree. C., then chilled to 4.degree. C. Colonies were transferred to nylon filters, and the cells lysed by standard methods known in the art. The filters were hybridized to a DNA probe generated from DNA fragments containing both VIP1A(a) and VIP2A(a) DNA sequences. Hybridization was performed overnight at 65.degree. C. using the hybridization conditions of Church and Gilbert (Church, G. M., and W. Gilbert, PNAS, 81:1991-1995 (1984)). Filters were washed with 2.times.SSC containing 0.1% SDS at 65.degree. C. and exposed to X-Ray film.
Of the 463 Bacillus strains screened, 55 strains were identified that hybridized to the VIP1A(a)/VIP2A(a) probe. DNA was isolated from 22 of these strains, and analyzed using a Southern blot with VIP1A(a)/VIP2A(a) DNA as probes. These strains were grouped into 8 classes based on their Southern blot pattern. Each class differed in Southern blot pattern from AB78. One class had a pattern identical to that of the VIP1A(a)/VIP2A(a) homologs from Bacillus thuringiensis var tenebrionis (see below). Each of the 22 strains was tested for activity against western corn rootworm (WCRW). Three strains, AB433, AB434, and AB435 were found to be active on WCRW. Western blot analysis using VIP2A(a) antisera revealed that strains AB6, AB433, AB434, AB435, AB444, and AB445 produce a protein(s) of equivalent size to VIP2A(a).
Notable among the strains identified was Bacillus thuringiensis strain AB6, (NRRL B-21060) which produced a VIP active against black cutworm (Agrotis ipsilon) as described in Example 15. Western blot analysis with polyclonal antisera to VIP2A(a) and polyclonal antisera to VIP1A(a) suggests that AB6 produces proteins similar to VIP2A(a) and VIP1A(a). Thus, AB6 may contain VIPs similar to VIP1A(a) and VIP2A(a), but with a different spectrum of insecticidal activity.
EXAMPLE 21
Cloning of a VIP1A(a)/VIP2A(a) Homolog from Bacillus thuringiensis var. tenebrionis
Several previously characterized Bacillus strains were tested for presence of DNA similar to VIP1A(a)/VIP2A(a) by Southern blot analysis. DNA from Bacillus strains AB78, AB88, GC91, HD-1 and ATCC 10876 was analyzed for presence of VIP1A(a)VIP2A(a) like sequences. DNA from Bt strains GC91 and HD-1, and the Bc strain ATCC 10876 did not hybridize to VIP2A(a)/VIP1A(a) DNA, indicating they lack DNA sequences similar to VIP1A(a)/VIP2A(a) genes. Similarly, DNA from the insecticidal strain AB88 (Example 16) did not hybridize to VIP1A(a)/VIP2A(a) DNA region, suggesting that the VIP activity produced by this strain does not result from VIP1A(a)VIP2A(a) homologs. In contrast, Bacillus thuringiensis var. tenebrionis (Btt) contained sequences that hybridized to the VIP1A(a)/VIP2A(a) region. Further analysis confirmed that Btt contains VIP1A(a)/VIP2A(a) like sequences.
To characterize the Btt homologs of VIP2A(a) and VIP1A(a), the genes encoding these proteins were cloned. Southern blot analysis identified a 9.5 kb Eco RI restriction fragment likely to contain the coding regions for the homologs. Genomic DNA was digested with Eco RI, and DNA fragments of approximately 9.5 kb in length were gel-purified. This DNA was ligated into pBluescript SK(+) digested with Eco RI, and transformed into E. coli to generate a plasmid library. Approximately 10,000 colonies were screened by colony hybridization for the presence of VIP2A(a) homologous sequences. Twenty eight positive colonies were identified. All twenty eight clones are identical, and contain VIP1A(a)/VIP2A(a) homologs. Clone pCIB7100 has been deposited in the Agricultural Research Service, Patent Culture Collection (NRRL), Northern Regional Research Center, 1815 North University Street, Peoria, Ill. 61604, USA, and given the Accession Number B-21322. Several subclones were constructed from pCIB7100. A 3.8 kb Xba I fragment from pCIB7100 was cloned into pBluescript SK(+) to yield pCIB7101. A 1.8 kb Hind III fragment and a 1.4 kb Hind III fragment from pCIB7100 were cloned into pBluescript SK(+) to yield pCIB7102 and pCIB7103, respectively. Subclones pCIB7101, pCIB7102 and pCIB7103 have been deposited in the Agricultural Research Service, Patent Culture Collection (NRRL), Northern Regional Research Center, 1815 North University Street, Peoria, Ill. 61604, USA, and given the Accession Numbers B-21323, B-21324 and B-21325 respectively.
The DNA sequence of the region of pCIB7100 containing the VIP2A(a)/VIP1A(a) homologs was determined by the dideoxy chain termination method (Sanger et al., 1977, Proc. Natl. Acad. Sci. USA 74:5463-5467). Reactions were performed using PRISM Ready Reaction Dye Deoxy Terminator Cycle Sequencing Kits and PRISM Sequenase.RTM. Terminator Double-Stranded DNA Sequencing Kits, and analyzed on an ABI model 373 automated sequencer. Custom oligonucleotides were used as primers to determine the DNA sequence in certain regions. The DNA sequence of this region is shown in SEQ ID NO:19.
The 4 kb region shown in SEQ ID NO:19 contains two open readings frames (ORFs), which encode proteins with a high degree of similarity to VIP1A(a) and VIP2A(a) proteins from strain AB78. The amino acid sequence of the VIP2A(a) homolog, designated as VIP2A(b) using the standardized nomenclature, is found at SEQ ID NO:20 and the amino acid sequence of the VIP1A(a) homolog, designated as VIP1A(b) using the standardized nomenclature, is disclosed at SEQ ID NO:21. The VIP2A(b) protein exhibits 91% amino acid identity to VIP2A(a) from AB78. An alignment of the amino acid sequences of the two VIP2 proteins is provided in Table 19. The VIP1A(b) protein exhibits 77% amino acid identity to VIP1A(a) from AB78. An alignment of these two VIP1 proteins is provided in Table 20. The alignment shown in Table 20 discloses the similarity between VIP1A(b) and VIP1A(a) from AB78. This alignment reveals that the amino terminal regions of the two VIP1 proteins share higher amino acid identity in the amino-terminal region than in the carboxy terminal region. In fact, the amino terminal two thirds (up to aa 618 of the VIP1A(b) sequence shown in Table 20) of the two proteins exhibit 91% identity, while the carboxy-terminal third (from aa 619-833 of VIP1A(b)) exhibit only 35% identity.
Western blot analysis indicated that Bacillus thuringiensis var. tenebrionis (Btt) produces both VIP1A(a) like and VIP2A(a) like proteins. However, these proteins do not appear to have activity against western corn rootworm. Bioassay for activity against western corn rootworm was performed using either a 24 h culture supernatant from Btt or E. coli clone pCIB7100 (which contains the entire region of the VIP1A(a)/VIP2A(a) homologs). No activity against western corn rootworm was detected in either case.
Given the similarity between the VIP2 proteins from Btt and AB78, the ability of VIP2A(b) from Btt to substitute for VIP2A(a) from AB78 was tested. Cells containing pCIB6206 (which produces AB78 VIP1A(a) but not VIP2A(a) protein) were mixed with Btt culture supernatant, and tested for activity against western corn rootworm. While neither Btt culture supernatant nor cells containing pCIB6206 had activity on WCRW, the mixture of Btt and pCIB6206 gave high activity against WCRW. Furthermore, additional bioassay showed that the Btt clone pCIB7100, which contains the Btt VIP1A(b)/VIP2A(b) genes in E. coli, also confers activity against WCRW when mixed with pCIB6206. Thus, the VIP2A(b) protein produced by Btt is functionally equivalent to the VIP2A(a) protein produced by AB78.
Thus, the ability to identify new strains with insecticidal activity by using VIP DNA as hybridization probes has been demonstrated. Furthermore, Bacillus strains that contain VIP1A(a)/VIP2A(a) like sequences, produce VIP1A(a)/VIP2A(a) like protein, yet demonstrate toxicity toward different insect pests. Similar methods can identify many more members of the VIP1/VIP2 family. Furthermore, use of similar methods can identify homologs of other varieties of VIPs (for example, the VIPs from AB88).
EXAMPLE 22
Fusion of VIP Proteins to make a Single Polypeptide
VIP proteins may occur in nature as single polypeptides, or as two or more interacting polypeptides. When an active VIP is comprised of two or more interacting protein chains, these protein chains can be produced as a single polypeptide chain from a gene resulting from the fusion of the two (or more) VIP coding regions. The genes encoding the two chains are fused by merging the coding regions of the genes to produce a single open reading frame encoding both VIP polypeptides. The composite polypeptides can be fused to produce the smaller polypeptide as the NH.sub.2 terminus of the fusion protein, or they can be fused to produce the larger of the polypeptides as the NH.sub.2 terminus of the fusion protein. A linker region can optionally be used between the two polypeptide domains. Such linkers are known in the art. This linker can optionally be designed to contain protease cleavage sites such that once the single fused polypeptide is ingested by the target insect it is cleaved in the linker region to liberate the two polypeptide components of the active VIP molecule.
VIP1A(a) and VIP2A(a) from B. cereus strain AB78 are fused to make a single polypeptide by fusing their coding regions. The resulting DNA has the sequence given in SEQ ID NO:22 with the encoded protein given in SEQ ID NO:23. In like manner, other fusion proteins may be produced.
The fusion of the genes encoding VIP1A(a) and VIP2A(a) is accomplished using standard techniques of molecular biology. The nucleotides deleted between the VIP1A(a) and VIP2A(a) coding regions are deleted using known mutagenesis techniques or, alternatively, the coding regions are fused using PCR techniques.
The fused VIP polypeptides can be expressed in other organisms using a synthetic gene, or partially synthetic gene, optimized for expression in the alternative host. For instance, to express the fused VIP polypeptide from above in maize, one makes a synthetic gene using the maize preferred codons for each amino acid, see for example patent application U.S. Ser. No. 07/951,715 herein incorporated by reference. Synthetic DNA sequences created according to these methods are disclosed in SEQ ID NO:17 (maize optimized version of the 100 kDa VIP1A(a) coding sequence), SEQ ID NO:18 (maize optimized version of the 80 kDa VIP1A(a) coding sequence) and SEQ ID NO:24 (maize optimized version of the VIP2A(a) coding sequence).
Synthetic VIP1 and VIP2 genes optimized for expression in maize can be fused using PCR techniques, or the synthetic genes can be designed to be fused at a common restriction site. Alternatively, the synthetic fusion gene can be designed to encode a single polypeptide comprised of both VIP1 and VIP2 domains.
Addition of a peptide linker between the VIP1 and VIP2 domains of the fusion protein can be accomplished by PCR mutagenesis, use of a synthetic DNA linker encoding the linker peptide, or other methods known in the art.
The fused VIP polypeptides can be comprised of one or more binding domains. If more than one binding domain is used in the fusion, multiple target pests are controlled using such a fusion. The other binding domains can be obtained by using all or part of other VIPs; Bacillus thuringiensis endotoxins, or parts thereof; or other proteins capable of binding to the target pest or appropriate biding domains derived from such binding proteins.
One example of a fusion construction comprising a maize optimized DNA sequence encoding a single polypeptide chain fusion having VIP2A(a) at the N-terminal end and VIP1A(a) at the C-terminal end is provided by pCIB5531. A DNA sequence encoding a linker with the peptide sequence PSTPPTPSPSTPPTPS (SEQ ID NO:47) has been inserted between the two coding regions. The sequence encoding this linker and relevant cloning sites is 5'-CCC GGG CCT TCT ACT CCC CCA ACT CCC TCT CCT AGC ACG CCT CCG ACA CCT AGC GAT ATC GGA TC C-3' (SEQ ID NO:48). Oligonucleotides were synthesized to represent both the upper and lower strands and cloned into a pUC vector following hybridization and phosphorylation using standard procedures. The stop codon in VIP2A(a) was removed using PCR and replaced by the BglII restriction site with a SmaI site. A translation fusion was made by ligating the Bam HI/PstI fragment of the VIP2A(a) gene from pCIB5522 (see Example 24), a PCR fragment containing the PstI-end fragment of the VIP2A(a) gene (identical to that used to construct pCIB5522), a synthetic linker having ends that would ligate with a blunt site at the 5' end and with BamHI at the 3' end and the modified synthetic VIP1A(a) gene from pCIB5526 described below (See SEQ ID NO:35). The fusion was obtained by a four way ligation that resulted in a plasmid containing the VIP2A(a) gene without a translation stop codon, with a linker and the VIP1A(a) coding region without the Bacillus secretion signal. The DNA sequence for this construction is disclosed in SEQ ID NO:49, which encodes the fusion protein disclosed in SEQ ID NO:50. A single polypeptide fusion where VIP1A(a) is at the N-terminal end and VIP2A(a) is at the C-terminal end can be made in a similar fashion. Furthermore, either one or both genes can be linked in a translation fusion with or without a linker at either the 5' or the 3' end to other molecules like toxin encoding genes or reporter genes.
EXAMPLE 23
Targeting of VIP2 to Plant Organelles
Various mechanisms for targeting gene products are known to exist in plants and the sequences controlling the functioning of these mechanisms have been characterized in some detail. For example, the targeting of gene products to the chloroplast is controlled by a signal sequence found at the amino-terminal end of various proteins. This signal is cleaved during chloroplast import, yielding the mature protein (e.g. Comai et al. J. Biol. Chem. 263:15104-15109 (1988)). These signal sequences can be fused to heterologous gene products such as VIP2 to effect the import of those products into the chloroplast (van den Broeck et al. Nature 313:358-363 (1985)). DNA encoding for appropriate signal sequences can be isolated from the 5' end of the cDNAs encoding the RUBISCO protein, the CAB protein, the EPSP synthase enzyme, the GS2 protein and many other proteins which are known to be chloroplast localized.
Other gene products are localized to other organelles such as the mitochondrion and the peroxisome (e.g. Unger et al. Plant Molec. Biol. 13:411-418 (1989)). The cDNAs encoding these products can also be manipulated to effect the targeting of heterologous gene products such as VIP2 to these organelles. Examples of such sequences are the nuclear-encoded ATPases and specific aspartate amino transferase isoforms for mitochondria. Similarly, targeting to cellular protein bodies has been described by Rogers et al. (Proc. Natl. Acad. Sci. USA 82:6512-6516 (1985)).
By the fusion of the appropriate targeting sequences described above to coding sequences of interest such as VIP2 it is possible to direct the transgene product to any organelle or cell compartment. For chloroplast targeting, for example, the chloroplast signal sequence from the RUBISCO gene, the CAB gene, the EPSP synthase gene, or the GS2 gene is fused in frame to the amino-terminal ATG of the transgene. The signal sequence selected should include the known cleavage site and the fusion constructed should take into account any amino acids after the cleavage site which are required for cleavage. In some cases this requirement may be fulfilled by the addition of a small number of amino acids between the cleavage site and the start codon ATG, or alternatively replacement of some amino acids within the coding sequence. Fusions constructed for chloroplast import can be tested for efficacy of chloroplast uptake by in vitro translation of in vitro transcribed constructions followed by in vitro chloroplast uptake using techniques described by (Bartlett et al. In: Edelmann et al. (Eds.) Methods in Chloroplast Molecular Biology, Elsevier. pp 1081-1091 (1982); Wasmann et al Mol. Gen. Genet. 205:446-453 (1986)). These construction techniques are well known in the art and are equally applicable to mitochondria and peroxisomes.
The above described mechanisms for cellular targeting can be utilized not only in conjunction with their cognate promoters, but also in conjunction with heterologous promoters so as to effect a specific cell targeting goal under the transcriptional regulation of a promoter which has an expression pattern different to that of the promoter from which the targeting signal derives.
A DNA sequence encoding a secretion signal is present in the native Bacillus VIP2 gene. This signal is not present in the mature protein which has the N-terminal sequence of LKITDKVEDF (amino acid residues 57 to 66 of SEQ ID NO:2). It is possible to engineer VIP2 to be secreted out of the plant cell or to be targeted to subcellular organelles such as the endoplasmic reticulum, vacuole, mitochondria or plastids including chloroplasts. Hybrid proteins made by fusion of a secretion signal peptide to a marker gene have been successfully targeted into the secretion pathway. (Itirriaga G. et al., The Plant Cell, 1:381-390 (1989), Denecke et al., The Plant Cell, 2:51-59 (1990). Amino-terminal sequences have been identified that are responsible for targeting to the ER, the apoplast, and extracellular secretion from aleurone cells (Koehler & Ho, Plant Cell 2:769-783 (1990)).
The presence of additional signals are required for the protein to be retained in the endoplasmic reticulum or the vacuole. The peptide sequence KDEL/HDEL at the carboxy-terminal of a protein is required for its retention in the endoplasmic reticulum (reviewed by Pelham, Annual Review Cell Biol., 5:1-23 (1989). The signals for retention of proteins in the vacuole have also been characterized. Vacuolar targeting signals may be present either at the amino-terminal portion, (Holwerda et al., The Plant Cell, 4:307-318 (1992), Nakamura et al., Plant Physiol., 101:1-5 (1993)), carboxy-terminal portion, or in the internal sequence of the targeted protein. (Tague et al., The Plant Cell, 4:307-318 (1992), Saalbach et al. The Plant Cell, 3:695-708 (1991)). Additionally, amino-terminal sequences in conjunction with carboxy-terminal sequences are responsible for vacuolar targeting of gene products (Shinshi et al. Plant Molec. Biol. 14:357-368 (1990)). Similarly, proteins may be targeted to the mitochondria or plastids using specific carboxy terminal signal peptide fusions (Heijne et al., Eur. J. Biochem., 180:535-545 (1989), Archer and Keegstra, Plant Molecular Biology, 23:1105-1115 (1993)).
In order to target VIP2, either for secretion or to the various subcellular organelles, a maize optimized DNA sequence encoding a known signal peptide(s) may be designed to be at the 5' or the 3' end of the gene as required. To secrete VIP2 out of the cell, a DNA sequence encoding the eukaryotic secretion signal peptide MGWSWIFLFLLSGAAGVHCL (SEQ ID NO:25) from U.S. patent application Ser. No. 08/267,641 or any other described in the literature (Itirriaga et al., The Plant Cell, 1:381-390 (1989), Denecke, et al., The Plant Cell, 2:51-59 (1990)) may be added to the 5' end of either the complete VIP2 gene sequence or to the sequence truncated to encode the mature protein or the gene truncated to nucleotide 286 or encoding a protein to start at amino acid residue 94 (methionine). To target VIP2 to be retained in the endoplasmic reticulum, a DNA sequence encoding the ER signal peptide KDEL/HDEL, in addition to the secretion signal, can be added to the 3' end of the gene. For vacuolar targeting a DNA sequence encoding the signal peptide SSSSFADSNPIRVTDRAAST (SEQ ID NO:3; Holwerda et al., The Plant Cell, 4:307-318 (1992)) can be designed to be adjacent to the secretion signal or a sequence encoding a carboxyl signal peptide as described by Dombrowski et al., The Plant Cell, 5:587-596 (1993) or a functional variation may be inserted at the 3' end of the gene. Similarly, VIP2 can be designed to be targeted to either the mitochondria or the plastids, including the chloroplasts, by inserting sequences in the VIP2 sequence described that would encode the required targeting signals. The bacterial secretion signal present in VIP2 may be retained or removed from the final construction.
One example of a construction which incorporates a eukaryotic secretion signal fused to a coding sequence for a VIP is provided by pCIB5528. Oligonucleotides corresponding to both the upper and lower strand of sequences encoding the secretion signal peptide of SEQ ID NO:25 was synthesized and has the sequence 5'-GGATCCACC ATG GGC TGG AGC TGG ATC TTC CTG TTC CTG CTG AGC GGC GCC GCGG GGC GTG CAC TGC CTGCAG-3' (SEQ ID NO:41). When hybridized, the 5' end of the secretion signal resembled "sticky-ends" corresponding to restriction sites BamHI and PstI. The oligonucleotide was hybridized and phosphorylated and ligated into pCIB5527 (construction described in Example 23A) which had been digested with BamHI/PstI using standard procedures. The resulting maize optimized coding sequence is disclosed in SEQ ID NO:42 which encodes the protein disclosed in SEQ ID NO:43. This encoded protein comprises the eukaryotic secretion signal in place of the Bacillus secretion signal.
One example of a construction which incorporates a vacuolar targetting signal fused to a coding sequence for a VIP is provided by pCIB5533. Oligonucleotides corresponding to both the upper and lower strand of sequences encoding the vacuolar targetting peptide of SEQ ID NO:3 was synthesized and has the sequence 5'-CCG CGG GCG TGC ACT GCC TCA GCA GCA GCA GCT TCG CCG ACA GCA ACC CCA TCC GCG TGA CCG ACC GCG CCG CCA GCA CCC TGC AG-3' (SEQ ID NO:44). When hybridized, the 5' end of the vacuolar targetting signal resembled "sticky-ends" corresponding to restriction sites SacII and PstI. The oligonucleotide was hybridized and phosphorylated and ligated into pCIB5528 (construction described above) which had been digested with SacII/PstI using standard procedures. The resulting maize optimized coding sequence is disclosed in SEQ ID NO:45 which encodes the protein disclosed in SEQ ID NO:46. This encoded protein comprises the vacuolar targetting peptide in addition to the eukaryotic secretion signal.
The VIP1 gene can also be designed to be secreted or targeted to subcellular organelles by similar procedures.
EXAMPLE 23A
Removal of Bacillus Secretion Signal from VIP1A(a) and VIP2A(a)
VIP1A(a) and VIP2A(a) are secreted during the growth of strain AB78. The nature of peptide sequences that act as secretion signals has been described in the literature (Simonen and Palva, Microbiological reviews, pg. 109-137 (1993)). Following the information in the above publication, the putative secretion signal was identified in both genes. In VIP1A(a) this signal is composed of amino acids 1-33 (See SEQ ID NO:5). Processing of the secretion signal probably occurs after the serine at amino acid 33. The secretion signal in VIP2A(a) was identified as amino acids 1-49 (See SEQ ID NO:2). N-terminal peptide analysis of the secreted mature VIP2A(a) protein revealed the N-terminal sequence LKITDKVEDFKEDK. This sequence is found beginning at amino acid 57 in SEQ ID NO:2. The genes encoding these proteins have been modified by removal of the Bacillus secretion signals.
A maize optimized VIP1A(a) coding region was constructed which had the sequences encoding the first 33 amino acids, i.e., the secretion signal, removed from its 5' end. This modification was obtained by PCR using an forward primer that contained the sequence 5'-GGA TCC ACC ATG AAG ACC AAC CAG ATC AGC-3' (SEQ ID NO:33), which hybridizes with the maize optimized gene (SEQ ID NO:26) at nucleotide position 100, and added a BamHI restriction site and a eukaryotic translation start site consensus including a start codon. The reverse primer that contained the sequence 5'-AAG CTT CAG CTC CTT G-3' (SEQ ID NO:34) hybridizes on the complementary strand at nucleotide position 507. A 527 bp amplification product was obtained containing the restriction sites BamHI at the 5' end and HindIII site at the 3' end. The amplification product was cloned into a T- vector (described in Example 24, below) and sequenced to ensure the correct DNA sequence. The BamHI/HindIII fragment was then obtained by restriction digest and used to replace the BamHI/HindIII fragment of the maize optimized VIP1A(a) gene cloned in the root-preferred promoter cassette. The construct obtained was designated pCIB5526. The maize optimized coding region for VIP1A(a) with the Bacillus secretion signal removed is disclosed as SEQ ID NO:35 and the encoded protein is disclosed as SEQ ID NO:36.
The gene encoding the processed form of VIP2A(a), i.e., a coding region with the secretion signal removed, was constructed by a procedure similar to that described for that used to construct the processed form of VIP1A(a), above. The modification was obtained by PCR using the forward primer 5'-GGA TCC ACC ATG CTG CAG AAC CTG AAG ATC AC -3' (SEQ ID NO:37). This primer hybridizes at nucleotide position 150 of the maize optimized VIP2A(a) gene (SEQ ID NO:27). A silent mutation has been inserted at nucleotide position 15 of this primer to obtain a PstI restriction site. The reverse primer has the sequence 5'-AAG CTT CCA CTC CTT CTC-3' (SEQ ID NO:38). A 259 bp product was obtained with HindIII restriction site at the 3' end. The amplification product was cloned into a T-vector, sequenced and ligated to a BamHI/HindIII digested root-preferred promoter cassette containing the maize optimized VIP2A(a). The construct obtained was designated pCIB5527. The maize optimized coding region for VIP2A(a) with the Bacillus secretion signal removed is disclosed as SEQ ID NO:39 and the encoded protein is disclosed as SEQ ID NO:40.
EXAMPLE 24
Construction and Cloning of the VIP1A(a) and VIP2A(a) Maize Optimized Genes
Design: The maize optimized genes were designed by reverse translation of the native VIP1A(a) and VIP2A(a) protein sequences using codons that are used most often in maize (Murray et al., Nucleic Acid Research, 17:477-498 (1989)). To facilitate cloning, the DNA sequence was further modified to incorporate unique restriction sites at intervals of every 200-360 nucleotides. VIP1A(a) was designed to be cloned in 11 such fragments and VIP2A(a) was cloned in 5 fragments. Following cloning of the individual fragments, adjacent fragments were joined using the restriction sites common to both fragments, to obtain the complete gene. To clone each fragment, oligonucleotides (50-85 nucleotides) were designed to represent both the upper and the lower strand of the DNA. The upper oligo of the first oligo pair was designed to have a 15 bp single stranded region at the 3' end which was homologous to a similar single stranded region of the lower strand of the next oligo pair to direct the orientation and sequence of the various oligo pairs within a given fragment. The oligos are also designed such that when the all the oligos representing a fragment are hybridized, the ends have single stranded regions corresponding to the particular restriction site to be formed. The structure of each oligomer was examined for stable secondary structures such as hairpin loops using the OLIGO program from NBI Inc. Whenever necessary, nucleotides were changed to decrease the stability of the secondary structure without changing the amino acid sequence of the protein. A plant ribosomal binding site consensus sequence, TAAACAATG (Joshi et al., Nucleic Acid Res., 15:6643-6653 (1987)) or eukaryotic ribosomal binding site concensus sequence CCACCATG (Kozak, Nucleic Acid Research, 12:857-872 (1984)) was inserted at the translational start codon of the gene.
Cloning: Oligos were synthesized by IDT Inc., and were supplied as lyophilized powders. They were resuspended at a concentration of 200 .mu.M. To 30 .mu.l of each oligo formamide was added a final concentration of 25-50% and the sample was boiled for two minutes before separation on a premade 10% polyacryamide/urea gel obtained from Novex. After electrophoresis, the oligo was detected by UV shadowing by placing the gel on a TLC plate containing a fluorescent indicator and exposing it to UV light. The region containing DNA of the correct size was excised and extracted from the polyacryamide by an overnight incubation of the minced gel fragment in a buffer containing 0.4M LiCl, 0.1 mM EDTA. The DNA was separated from the gel residue by centrifugation through a Millipore UFMC filter. The extracted DNA was ethanol precipitated by the addition of 2 volumes of absolute alcohol. After centrifugation, the precipitate was resuspended in dH.sub.2 O at a concentration of 2.5 .mu.M. Fragments were cloned either by hybridization of the oligos and ligation with the appropriate vector or by amplification of the hybridized fragment using a equimolar mixture of all the oligos for a particular fragment as a template and end-specific PCR primers.
Cloning by hybridization and ligation: Homologous double stranded oligo pairs were obtained by mixing 5 .mu.l of the upper and of the lower oligo for each oligo pair with buffer containing 1.times.polynucleotide kinase (PNK) buffer (70 mM Tris-HCl (pH 7.6), 10 mM MgCl.sub.2, 5 mM dithiothreitol (DTT)), 50 mM KCl, and 5% formamide in a final volume of 50 .mu.l. The oligos were boiled for 10 minutes and slow cooled to 37.degree. C. or room temperature. 10 .mu.l was removed for analysis on a 4% agarose in a TAE buffer system (Metaphore.RTM.; FMC). Each hybridized oligo pair was kinased by the addition of ATP at a final concentration of 1 mM, BSA at a final concentration of 100 .mu.g per ml and 200 units of polynucleotide kinase and 1 .mu.l of 10.times.PNK buffer in a volume of 10 .mu.l. Following hybridization and phosphorylation, the reaction was incubated at 37.degree. C. for 2 hours to overnight. 10 .mu.l of each of the oligo pairs for a particular fragment, were mixed in a final volume of 50 .mu.l. The oligo pairs were hybridized by heating at 80.degree. C. for 10 minutes and slow cooling to 37.degree. C. 2 .mu.l of oligos was mixed with about 100 ng of an appropriate vector and ligated using a buffer containing 50 mM Tris-HCl (pH 7.8), 10 mM MgCl.sub.2, 10 mM DTT, 1 mM ATP. The reaction was incubated at room temp. for 2 hours to overnight and transformed into DH5.alpha. strain of E.coli, plated on L-plates containing ampicillin at a concentration of 100 .mu.g/ml using standard procedures. Positive clones were further characterized and confirmed by PCR miniscreen described in detail in U.S. patent application Ser. No. 07/951,715 using the universal primers "Reverse" and M13 "-20" as primers. Positive clones were identified by digestion of DNA with appropriate enzymes followed by sequencing. Recombinants that had the expected DNA sequence were then selected for further work.
PCR Amplification and cloning Into T-vector:
PCR amplification was carried out by using a mixture of all the oligomers that represented the upper and the lower strand of a particular fragment (final concentration 5 mM each) as template, specific end primers for the particular fragment (final concentration 2 .mu.M) 200 .mu.M of each dATP, dTTP, dCTP and dGTP, 10 mM Tris-HCl (pH 8.3), 50 mM KCl, 1.5 mM MgCl.sub.2,0.01% gelatin and 5 units of Taq polymerase in a final reaction volume of 50 .mu.l. The amplification reaction was carried out in a Perkin Elmer thermocycler 9600 by incubation at 95.degree. C. for 1 min (1 cycle ), followed by 20 cycles of 95.degree. C. for 45 sec., 50 .degree. C. for 45 sec., 72.degree. C. for 30 sec. Finally the reaction was incubated for 5 min at 72.degree. C. before analyzing the product. 10 .mu.l of the reaction was analyzed on a 2.5% Nusieve (FMC) agarose gel in a TAE buffer system. The correct size fragment was gel purified and used for cloning into a PCR cloning vector or T-vector. T-vector construction was as described by Marchuk et al., Nucleic Acid Research. 19:1154 (1991). pBluescriptsk+ (Stratagene.RTM., Calif.) was used as the parent vector. Transformation and identification of the correct clone was carried out as described above.
Fragments 1, 3, 4, 5, 6, 8, and 9 of VIP1A(a) and fragments 2 and 4 of VIP2A(a) were obtained by cloning of PCR amplification products; whereas, fragments 2, 7, 10 and 11 of VIP1A(a) and fragments 1, 3, and 5 of VIP2A(a) were obtained by hybridization/ligation.
Once fragments with the desired sequence were obtained, the complete gene was assembled by cloning together adjacent fragments. The complete gene was resequenced and tested for activity against WCRW before moving it into plant expression vectors containing the root preferred promoter (disclosed in U.S. patent application Ser. No. 08/017,209, herein incorporated by reference) and the rice actin promoter.
One such plant expression vector is pCIB5521. The maize optimized VIP1A(a) coding region (SEQ ID NO:26) was cloned in a plant expression vector containing the root preferred promoter at the 5' of the gene with the PEP Carboxylase intron #9 followed by the 35S terminator at the 3' end. The plasmid also contains sequences for ampicillin resistance from the plasmid pUC 19. Another plant expression vector is pCIB5522, which contains the maize optimized VIP2A(a) coding region (SEQ ID NO:27) fused to the root preferred promoter at the 5' of the gene with the PEP Carboxylase intron #9 followed by the 35S terminator at the 3' end.
EXAMPLE 25
NAD Affinity Chromatography
A purification strategy was used based on the affinity of VIP2 for the substrate NAD. The supernatant from the pH 3.5 sodium citrate buffer treatment described in Example 4 was dialyzed in 20 mM TRIS pH 7.5 overnight. The neutralized supernatant was added to an equal volume of washed NAD agarose and incubated with gentle rocking at 4.degree. C. overnight. The resin and protein solution were added to a 10 ml disposable polypropylene column and the protein solution allowed to flow out. The column was washed with 5 column volumes of 20 mM TRIS pH 7.5 then washed with 2-5 column volumes of 20 mM TRIS pH 7.5, 100 mM NaCl, followed by 2-5 column volumes of 20 mM TRIS 7.5. The VIP proteins were eluted in 20 mM TRIS pH 7.5 supplemented with 5 mM NAD. Approximately 3 column volumes of the effluent were collected and concentrated in a Centricon -10. Yield is typically about 7-15 .mu.g of protein per ml of resin.
When the purified proteins were analyzed by SDS-PAGE followed by silver staining, two polypeptides were visible, one with Mr of approximately 80,000 and one with Mr of approximately 45,000. N-terminal sequencing revealed that the Mr 80,000 protein corresponded to a proteolytically processed form of VIP1A(A) and the Mr 45,000 form corresponded to a proteolytically processed form of VIP2A(a). The co-purification of VIP1A(a) with VIP2A(a) indicates that the two proteins probably form a complex and have protein-protein interacting regions. VIP1A(a) and VIP2A(a) proteins purified in this manner were biologically active against western corn rootworm.
EXAMPLE 26
Expression of Maize Optimized VIP1A(a) and VIP2A(a)
E. coli strains containing different plasmids comprising VIP genes were assayed for expression of VIPs. E. coli strains harboring the individual plasmids were grown overnight in L-broth and expressed protein was extracted from the culture as described in Example 3, above. Protein expression was assayed by Western Blot analysis using antibodies developed using standard methods known in the art, similar to those described in Example 12, above. Also, insecticidal activity of the expressed proteins were tested against Western corn rootworm according to the method in Example 3, above. The results of the E. coli expression assays are described below.
The DNA from these plasmids was used to transiently express the VIPs in a maize protoplast expression system. Protoplasts were isolated from maize 2717 Line 6 suspension cultures by digestion of the cell walls using Cellulase RS and Macerase R10 in appropriate buffer. Protoplasts were recovered by sieving and centrifugation. Protoplasts were transformed 10 by a standard direct gene transfer method using approximately 75 .mu.g plasmid DNA and PEG-40. Treated protoplasts were incubated overnight in the dark at room temperature. Analysis of VIP expression was accomplished on protoplast explants by Western blot analysis and insecticidal activity against Western corn rootworm as described above for the expression in E. coli. The results of the maize protoplast expression assays are described below.
The expression data obtained with both E. coli and maize protoplasts show that the maize optimized VIP1A(a) and VIP2A(a) genes make the same protein as the native VIP1A(a) and VIP2A(a) genes, respectively, and that the proteins encoded by the maize optimized genes are functionally equivalent to the proteins encoded by the native genes.
All publications and patent applications mentioned in this specification are indicative of the level of skill of those skilled in the art to which this invention pertains. All publications and patent applications are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference.
The following deposits have been made at Agricultural Research Service, Patent Culture Collection (NRRL), Northern, Regional Research Center, 1815 North University Street, Peoria, Ill. 61604, USA:
1. E. coli PL2 Accession No. NRRL B-21221N
2. E. coli pCIB6022 Accession No. NRRL B-21222
3. E. coli pCIB6023 Accession No. NRRL B-21223N
4. Bacillus thuringiensis HD73-78VIP Accession No. NRRL B-21224
5. Bacillus thuringiensis AB88 Accession No. NRRL B-21225
6. Bacillus thuringiensis AB359 Accession No. NRRL B-21226
7. Bacillus thuringiensis AB289 Accession No. NRRL B-21227
8. Bacillus sp. AB59 Accession No. NRRL B-21228
9. Bacillus sp. AB294 Accession No. NRRL B-21229
10. Bacillus sp. AB256 Accession No. NRRL B-21230
11. E. coli P5-4 Accession No. NRRL B-21059
12. E. coli P3-12 Accession No. NRRL B-21061
13. Bacillus cereus AB78 Accession No. NRRL B-21058
14. Bacillus thuringiensis AB6 Accession No. NRRL B-21060
15. E. coli pCIB6202 Accession No. NRRL B-21321
16. E. coli pCIB7100 Accession No. NRRL B-21322
17. E. coli pCIB7101 Accession No. NRRL B-21323
18. E. coli pCIB7102 Accession No. NRRL B-21324
19. E. coli pCIB7102 Accession No. NRRL B-21325
20. E. coli pCIB7104 Accession No. NRRL B-21422
21. E. coli pCIB7107 Accession No. NRRL B-21423
22. E. coli pCIB7108 Accession No. NRRL B-21438
23. Bacillus thuringiensis AB424 Accession No. NRRL B-21439
Although the foregoing invention has been described in some detail by way of illustration and example for purposes of clarity of understanding, it will be obvious that certain changes and modifications may be practiced within the scope of the appended claims.
Claims
What is claimed is:
1. A substantially pure nucleotide sequence which encodes an insecticidal protein secreted during the vegetative growth phase of Bacillus spp. and components thereof, wherein said protein is not the mosquitocidal toxin from B. spaericus SSII-1.
2. The nucleotide sequence of claim 1 wherein said sequence has been optimized for expression in a microorganism.
3. The nucleotide sequence of claim 1, wherein said sequence is optimized for expression in a plant.
4. The nucleotide sequence of claim 1, wherein said sequence lacks the Bacillus secretion signal.
5. The nucleotide sequence of claim 1, wherein said Bacillus is selected from a Bacillus thuringensis and B. cereus.
6. The nucleotide sequence of claim 1, wherein said Bacillus is Bacillus cereus having Accession No. NRRL B-21058.
7. The nucleotide sequence of claim 5, wherein said sequence is optimized for expression in a plant.
8. The nucleotide sequence of claim 6, wherein said sequence is optimized for expression in a plant.
9. A nucleotide sequence encoding an insecticidal protein, wherein said sequence is selected from the group consisting of SEQ ID NO:4, SEQ ID NO:6, SEQ ID NO:17, SEQ ID NO:18, SEQ ID NO:24, SEQ ID NO:26, SEQ ID NO:27, SEQ ID NO:28, SEQ ID NO:30, SEQ ID NO:31, SEQ ID NO:35, SEQ ID NO:39, SEQ ID NO:42 and SEQ ID NO:45.
10. A nucleotide sequence encoding an insecticidal protein, wherein said protein has the sequence selected from the group consisting of SEQ ID NO:7, SEQ ID NO:5, SEQ ID NO:2, SEQ ID NO:20, SEQ ID NO:21, SEQ ID NO:29, SEQ ID NO:32, SEQ ID NO:36, SEQ ID NO:40, SEQ ID NO:43, SEQ ID NO:46 and SEQ ID NO:50.
11. The nucleotide sequence of claim 10, wherein said sequence is optimized for expression in a plant.
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