US 5,539,092 AGrant
Cyanobacterial and Plant Acetyl-CoA Carboxylase
Issue Date:1996-07-23
•9 Claims
•16 Drawing Sheets
Abstract
The present invention provides isolated and purified polynucleotides that encode plant and cyanobacterial polypeptides that participate in the carboxylation of acetyl-CoA. Isolated cyanobacterial and plant polypeptides that catalyze acetyl-CoA carboxylation are also provided. Processes for altering acetyl-CoA carboxylation, increasing herbicide resistance of plants and identifying herbicide resistant variants of acetyl-CoA carboxylase are also provided.
Metadata
Assignee
- ARCH Development Corporation
Inventors
- Robert Haselkorn
- Piotr Gornicki
Application Information
Application Number:US 9567003
Filing Date:1992-10-02
Priority Date:1992-10-02
Art Unit:184
Classifications
IPC:
C07H 2104
Field of Search:
80053643593553020523.2;23.6;23.7;24.17.4;7.6;29;69.1;172.3;240.4;252.3;257;320.1;9469;10;14;64;66;67;78;79;90300;370
Patent Drawings (16 sheets)
Description
DESCRIPTION
1. Technical Field of the Invention
The present invention relates to polynucleotides and polypeptides of acetyl-CoA carboxylase in cyanobacteria and plants. Polynucleotides encoding acetyl-CoA carboxylase have use in conferring herbicide resistance and in determining the herbicide resistance of plants in a breeding program.
2. Background of the Invention
Acetyl-CoA carboxylase (ACC) is the first enzyme of the biosynthetic pathway to fatty acids. It belongs to a group of carboxylases that use biotin as cofactor and bicarbonate as a source of the carboxyl group. ACC catalyzes the addition of CO.sub.2 to acetyl-CoA to yield malonyl-CoA in two steps as shown below.
First, biotin becomes carboxylated at the expense of ATP. The carboxyl group is then transferred to Ac-CoA [Knowles, 1989]. This irreversible reaction is the committed step in fatty acid synthesis and is a target for multiple regulatory mechanisms. Reaction (1) is catalyzed by biotin carboxylase (BC); reaction (2) by transcarboxylase (TC); BCCP=biotin carboxyl carrier protein.
ACC purified from E. coli contains three distinct, separable components.: biotin carboxylase (BC), a dimer of 49-kD monomers, biotin carboxyl carrier protein (BCCP) a dimer of 17-kD monomers and transcarboxylase (TC), a tetramer containing two each of 33-kD and 35-kD subunits. The biotin prosthetic group is covalently attached to the .gamma.-amino group of a lysine residue of BCCP. The primary structure of E. coli BCCP and BC is known (fabE and fabG genes, respectively, have been cloned and sequenced) [Alix, 1989; Maramatsu, et al., 1989; Li, et al., 1992]. In bacteria, fatty acids are primarily precursors of phospholipids rather than storage fuels, and so ACC activity is coordinated with cell growth and division.
Rat and chicken ACC consist of a dimer of about 265 kD (rat has also a 280 kD isoform) subunits that contains all of the bacterial enzyme activities. Both mammalian and avian ACC are cytoplasmic enzymes and their substrate is transported out of mitochondria via citrate. ACC content and/or activity varies with the rate of fatty acid synthesis or energy requirements in different nutritional, hormonal and developmental states. ACC mRNA is transcribed using different promoters and can be regulated by alternative splicing. ACC catalytic activity is regulated allosterically by a number of metabolites and by reversible phosphorylation of the enzyme. The primary structure of rat and chicken enzymes, and the primary structure of the 5'-untranslated region of mRNA have been deduced from cDNA sequences [Lopez-Casillas, et al., 1988; Takai, et al., 1988]. The primary structure of yeast ACC has also been determined [Feel, et al., 1992].
Studies on plant ACC are far less advanced [Harwood, 1988]. It was originally thought that plant ACC consisted of low molecular weight dissociable subunits similar to those of bacteria. Those results appeared to be due to degradation of the enzyme during purification. More recent results indicate that the wheat enzyme, as well as those from parsley and rape, are composed of two about 220 kD monomers, similar to the enzyme from rat and chicken [Harwood, 1988; Egin-Buhler, et al., 1983; Wurtelle, et al., 1990; Slabas, et al., 1985]. The plant ACC is located entirely in the stroma of plastids, where all plant fatty acid synthesis occurs. No plant gene encoding ACC has been reported to date. The gene must be nuclear because no corresponding sequence is seen in the complete chloroplast DNA sequences of tobacco, liverwort or rice. ACC, like the vast majority of chloroplast proteins which are encoded in nuclear DNA, must be synthesized in the cytoplasm and then transported into the chloroplast, probably requiring a chloroplast transport sequence. Although the basic features of plant ACC must be the same as those of prokaryotic and other eucaryotic ACCs, significant differences can be also expected due, for example, to differences in plant cell metabolism and ACC cellular localization.
Structural similarities deduced from the available amino acid sequences suggest strong evolutionary conservation among biotin carboxylases and biotin carboxylase domains of all biotin-dependent carboxylases. On the contrary, the BCCP domains show very little conservation outside the sequence E(A/V)MKM (lysine residue is biotinylated) which is found in all biotinylated proteins including pyruvate carboxylase and propionyl-CoA carboxylase [Knowles, 1989; Samols, et al., 1988]. It is likely that the three functional domains of ACC located in E. coli on separate polypeptides are present in carboxylases containing two (human propionyl-CoA carboxylase) or only one (yeast pyruvate carboxylase, mammalian, avian and probably also plant ACC) polypeptide as a result of gene fusion during evolution.
Several years ago it was shown that aryloxyphenoxypropionates and cyclohexanediones, powerful herbicides effective against monocot weeds, inhibit fatty acid biosynthesis in sensitive plants. Recently it has been determined that ACC is the target enzyme for both of these classes of herbicide. Dicotyledonous plants are resistant to these compounds, as are other eukaryotes and prokaryotes. The mechanisms of inhibition and resistance of the enzyme are not known [Lichtenthaler, 1990].
It has occurred to others that the evolutionary relatedness of cyanobacteria and plants make the former useful sources of cloned genes for the isolation of plant cDNAs. For example, Pecker et al used the cloned gene for the enzyme phytoene desaturase, which functions in the synthesis of carotenoids, from cyanobacteria as a probe to isolate the cDNA for that gene from tomato [Pecker, et al., 1992].
BRIEF SUMMARY OF THE INVENTION
In one aspect the present invention provides an isolated and purified polynucleotide of from about 1350 to about 40,000 base pairs that encodes a polypeptide having the ability to catalyze the carboxylation of a biotin carboxyl carrier protein of a cyanobacterium. Preferably, that polypeptide is a subunit of acetyl-CoA carboxylase and participates in the carboxylation of acetyl-CoA. In a preferred embodiment, a cyanobacterium is Anabaena or Synechococcus. The biotin carboxyl carrier protein preferably includes the amino acid residue sequence shown in SEQ ID NO:111 or a functional equivalent thereof.
In another preferred embodiment, the polypeptide has the amino acid residue sequence of FIG. 1 or FIG. 2. The polynucleotide preferably includes the DNA sequence of SEQ ID NO:1, the DNA sequence of SEQ ID NO:1 from about nucleotide position 1300 to about nucleotide position 2650 or the DNA sequence of SEQ ID NO:5.
In another aspect, the present invention provides an isolated and purified polynucleotide of from about 480 to about 40,000 base pairs that encodes a biotin carboxyl carrier protein of a cyanobacterium and, preferably Anabaena. The biotin carboxyl carrier protein preferably includes the amino acid residue sequence of SEQ ID NO:111 and the polynucleotide preferably includes the DNA sequence of SEQ ID NO:110.
Another polynucleotide provided by the present invention encodes a plant polypeptide having the ability to catalyze the carboxylation of acetyl-CoA. A plant polypeptide is preferably (1) a monocotyledonous plant polypeptide such as a wheat, rice, maize, barley, rye, oats or timothy grass polypeptide or (2) a dicotyledonous plant polypeptide such as a soybean, rape, sunflower, tobacco, Arabiodopsis, petunia, Canola, pea, bean, tomato, potato, lettuce, spinach, alfalfa, cotton or carrot polypeptide. Preferably, that polypeptide is a subunit of ACC and participates in the carboxylation of acetyl-CoA.
Such a polynucleotide preferably includes the nucleotide sequence of SEQ ID NO:108 and encodes the amino acid residue sequence of SEQ ID NO:109.
In yet another aspect, the present invention provides an isolated and purified DNA molecule comprising a promoter operatively linked to a coding region that encodes (1) a polypeptide having the ability to catalyze the carboxylation of a biotin carboxyl carrier protein of a cyanobacterium, (2) a biotin carboxyl carrier protein of a cyanobacterium or (3) a plant polypeptide having the ability to catalyze the carboxylation of acetyl-CoA, which coding region is operatively linked to a transcription-terminating region, whereby said promoter drives the transcription of said coding region.
In another aspect, the present invention provides an isolated polypeptide having the ability to catalyze the carboxylation of a biotin carboxyl carrier protein of a cyanobacterium such as Anabaena or Synechococcus. Preferably a biotin carboxyl carrier protein includes the amino acid sequence of SEQ ID NO:111 and the polypeptide has the amino acid residue sequence of FIG. 1 or FIG. 2 (SEQ ID NO:5 and SEQ ID NO:6).
The present invention also provides (1) an isolated and purified biotin carboxyl carrier protein of a cyanobacterium such as Anabaena, which protein includes the amino acid residue sequence of SEQ ID NO:111 and (2) an isolated and purified plant polypeptide having a molecular weight of about 220 kD, dimers of which have the ability to catalyze the carboxylation of acetyl-CoA.
In yet another aspect, the present invention provides a process of increasing the herbicide resistance of a monocotyledonous plant comprising transforming the plant with a DNA molecule comprising a promoter operatively linked to a coding region that encodes a herbicide resistant polypeptide having the ability to catalyze the carboxylation of acetyl-CoA, which coding region is operatively linked to a transcription-terminating region, whereby the promoter is capable of driving the transcription of the coding region in a monocotyledonous plant.
Preferably, a polypeptide is an acetyl-CoA carboxylase enzyme and, more preferably, a dicotyledonous plant acetyl-CoA carboxylase. In a preferred embodiment, a coding region includes the DNA sequence of SEQ ID NO:108 and a promoter is CaMV35.
The present invention also provides a transformed plant produced in accordance with the above process as well as a transgenic plant and a transgenic plant seed having incorporated into its genome a transgene that encodes a herbicide resistant polypeptide having the ability to catalyze the carboxylation of acetyl-CoA.
In yet another aspect, the present invention provides a process of altering the carboxylation of acetyl-CoA in a cell comprising transforming the cell with a DNA molecule comprising a promoter operatively linked to a coding region that encodes a plant polypeptide having the ability to catalyze the carboxylation of acetyl-CoA, which coding region is operatively linked to a transcription-terminating region, whereby the promoter is capable of driving the transcription of the coding region in the cell.
In a preferred embodiment, a cell is a cyanobacterium or a plant cell and a plant polypeptide is a monocotyledonous plant acetyl-CoA carboxylase enzyme such as wheat acetyl-CoA carboxylase enzyme. The present invention also provides a transformed cyanobacterium produced in accordance with such a process.
The present invention still further provides a process for determining the inheritance of plant resistance to herbicides of the aryloxyphenocypropionate or cyclohexanedione class, which process comprises the steps of:
(a) measuring resistance to herbicides of the aryloxyphenocypropionate or cyclohexanedione class in a parental plant line and in progeny of the parental plant line;
(b) purifying DNA from said parental plant line and the progeny;
(c) digesting the DNA with restriction enzymes to form DNA fragments;
(d) fractionating the fragments on a gel;
(e) transferring the fragments to a filter support;
(f) annealing the fragments with a labelled RFLP probe consisting of a DNA molecule that encodes acetyl-CoA carboxylase or a portion thereof; and
(g) detecting the presence of complexes between the fragments and the RFLP probe; and
(h) correlating the herbicide resistance of step (a) with the complexes of step (g) and thereby the inheritance of herbicide resistance.
Preferably, the acetyl-CoA carboxylase is a dicotyledonous plant acetyl-CoA carboxylase enzyme or a mutated monocotyledonous plant acetyl-CoA carboxylase that confers herbicide resistance or a hybrid acetyl-CoA carboxylase comprising a portion of a dicotyledonous plant acetyl-CoA carboxylase, a portion of a dicotyledonous plant acetyl-CoA carboxylase or one or more domains of a cyanobacterial acetyl-CoA carboxylase.
In still yet another aspect, the present invention provides a process for identifying herbicide resistant variants of a plant acetyl-CoA carboxylase comprising the steps of:
(a) transforming cyanobacteria with a DNA molecule that encodes a monocotyledonous plant acetyl-CoA carboxylase enzyme to form transformed cyanobacteria;
(b) inactivating cyanobacterial acetyl-CoA carboxylase;
(c) exposing the transformed cyanobacteria to a herbicide that inhibits acetyl-CoA carboxylase activity;
(d) identifying transformed cyanobacteria that are resistant to the herbicide; and
(e) characterizing DNA that encodes acetyl-CoA carboxylase from the cyanobacteria of step (d).
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings which form a portion of the specification:
FIG. 1 shows the complete nucleotide sequence (SEQ ID NO:1) of a HindIII fragment that includes the fabG gene coding biotin carboxylase from the cyanobacterium Anabaena 7120, along with the amino acid sequence (SEQ ID NO:2-4) deduced from the coding sequence of the DNA.
FIG. 2 shows the nucleotide sequence (SEQ ID NO:5) of the coding region of the fabG gene from the cyanobacterium Anacystis nidulans R2, along with the amino acid sequence deduced from the coding sequence (SEQ ID NO:6) of the DNA.
FIGS. 3A-3E show an alignment of the amino acid sequences (SEQ ID NOS:6-107 and 109) of the BC proteins from both cyanobacteria and from E. coli, the BCCP proteins from Anabaena and from E. coli, along with the ACC enzymes from rat and chicken and several other biotin-containing carboxylases. Stars indicate positions that are identical in all sequences or all but one. The conventional one letter abbreviations for amino acids are used. The BC domains are indicated by a solid underline, the BCCP domains by a dashed underline. The symbol # indicates sequences not related to BC and, therefore, not considered in the alignment. The wheat ACC sequence deduced from the sequence of our cloned cDNA fragment is on the top line. Abbreviations used in the Figure are: Wh ACC, wheat ACC; Rt, rat; Ch, chicken; Yt, yeast; Sy ACC, Synechococcus BC; An ACC, Anabaena BC and BCCP proteins; EC ACC, E. coli BC and BCCP; Hm PCCA, human propionyl CoA carboxylase; Rt PCCA, rat propionyl CoA carboxylase; Yt PC, yeast pyruvate carboxylase.
FIG. 4 shows the conserved amino acid sequences used to design primers for the PCR to amplify the BC domain of ACC from wheat. The sequences of the oligonucleotide primers (SEQ ID NOS:112 and 113) are also shown. In this and other figures showing primer sequences, A means adenine, C means cytosine, G means guanine, T means thymine, N means all four nucleotides, Y means T or C, R means A or G, K means G or T, M means A or C, W means A or T, and H means A, C or T.
FIG. 5 shows the sequences of the oligonucleotides (SEQ ID NOS:114 and 115) used as primers for the PCR used to amplify the region of wheat ACC cDNA between the BC and BCCP domains.
FIG. 6 shows the nucleotide sequence (SEQ ID NO:108) of a portion of the wheat cDNA corresponding to ACC. The amino acid sequence (SEQ ID NO:109) deduced from the nucleotide sequence is also shown. The underlined sequences correspond to the primer sites shown in FIG. 5. A unique sequence was found for the BC domain, suggesting that a single mRNA was the template for the final amplified products. For the sequence between the BC and BCCP domains, three different variants were found among four products sequenced, suggesting that three different gene transcripts were among the amplified products. This is not unexpected because wheat is hexaploid, i.e. it has three pairs of each chromosome.
FIG. 7 shows the sequences (SEQ ID NOS:115 and 116) of the oligonucleotides used as primers to amplify most of the fabE gene encoding the biotin carboxyl carrier protein from DNA of Anabaena.
FIG. 8 shows the nucleotide sequence (SEQ ID NO:110) of a PCR product corresponding to a portion of the fabE gene encoding about 75% of the biotin carboxyl carrier protein from the cyanobacterium Anabaena, along with the amino acid sequence (SEQ ID NO:111) deduced from the coding sequence. The underlined sequences correspond to the primer sites shown in FIG. 7.
DETAILED DESCRIPTION OF THE INVENTION
I. Definitions
The following words and phrases have the meanings set forth below.
Expression: The combination of intracellular processes, including transcription and translation undergone by a coding DNA molecule such as a structural gene to produce a polypeptide.
Promoter: A recognition site on a DNA sequence or group of DNA sequences that provide an expression control element for a structural gene and to which RNA polymerase specifically binds and initiates RNA synthesis (transcription) of that gene.
Regeneration: The process of growing a plant from a plant cell (e.g. plant protoplast or explant).
Structural gene: A gene that is expressed to produce a polypeptide.
Transformation: A process of introducing an exogenous DNA sequence (e.g. a vector, a recombinant DNA molecule) into a cell or protoplast in which that exogenous DNA is incorporated into a chromosome or is capable of autonomous replication.
Transformed cell: A cell whose DNA has been altered by the introduction of an exogenous DNA molecule into that cell.
Transgenic cell: Any cell derived or regenerated from a transformed cell or derived from a transgenic cell. Exemplary transgenic cells include plant calli derived from a transformed plant cell and particular cells such as leaf, root, stem, e.g. somatic cells, or reproductive (germ) cells obtained from a transgenic plant.
Transgenic plant: A plant or progeny thereof derived from a transformed plant cell or protoplast, wherein the plant DNA contains an introduced exogenous DNA molecule not originally present in a native, non-transgenic plant of the same strain. The terms "transgenic plant" and "transformed plant" have sometimes been used in the art as synonymous terms to define a plant whose DNA contains an exogenous DNA molecule. However, it is thought more scientifically correct to refer to a regenerated plant or callus obtained from a transformed plant cell or protoplast as being a transgenic plant, and that usage will be followed herein.
Vector: A DNA molecule capable of replication in a host cell and/or to which another DNA segment can be operatively linked so as to bring about replication of the attached segment. A plasmid is an exemplary vector.
Certain polypeptides are disclosed herein as amino acid residue sequences. Those sequences are written left to right in the direction from the amino to the carboxy terminus. In accordance with standard nomenclature, amino acid residue sequences are denominated by either a single letter or a three letter code as indicated below.
The present invention provides polynucleotides and polypeptides relating to a whole or a portion of acetyl-CoA carboxylase (ACC) of cyanobacteria and plants as well as processes using those polynucleotides and polypeptides.
II. Polynucleotides
As used herein the term "polynucleotide" means a sequence of nucleotides connected by phosphodiester linkages. A polynucleotide of the present invention can comprise from about 2 to about several hundred thousand base pairs. Preferably, a polynucleotide comprises from about 5 to about 150,000 base pairs. Preferred lengths of particular polynucleotides are set hereinafter.
A polynucleotide of the present invention can be a deoxyribonucleic acid (DNA) molecule or a ribonucleic acid (RNA) molecule. Where a polynucleotide is a DNA molecule, that molecule can be a gene or a cDNA molecule. Nucleotide bases are indicated herein by a single letter code: adenine (A), guanine (G), thymine (T), cytosine (C), and uracil (U).
A. Cyanobacteria
In one embodiment, the present invention contemplates an isolated and purified polynucleotide of from about 1350 to about 40,000 base pairs that encodes a polypeptide having the ability to catalyze the carboxylation of a biotin carboxyl carrier protein of a cyanobacterium.
Preferably, a biotin carboxyl carrier protein (BCCP) is derived from a cyanobacterium such as Anabaena or Synechococcus. A preferred Anabaena is Anabaena 7120. A preferred Synechococcus is Anacystis nidulans R2 (Synechococcus sp. strain pcc7942). A biotin carboxyl carrier protein preferably includes the amino acid residue sequence shown in SEQ ID NO:111 or a functional equivalent thereof.
Preferably, a polypeptide is a biotin carboxylase enzyme of a cyanobacterium, which enzyme is a subunit of acetyl-CoA carboxylase and participates in the carboxylation of acetyl-CoA. In a preferred embodiment, a polypeptide encoded by such a polynucleotide has the amino acid residue sequence of FIG. 1 or FIG. 2 (SEQ ID NO:5 and SEQ ID NO:6), or a functional equivalent of those sequences.
A polynucleotide preferably includes the DNA sequence of SEQ ID NO:1 (FIG. 1) or the DNA sequence of SEQ ID NO:1 (FIG. 1) from about nucleotide position 1300 to about nucleotide position 2650.
The polynucleotide of SEQ ID NO:1 contains a gene that encodes the enzyme biotin carboxylase (BC) from the cyanobacterium Anabaena. This gene was cloned in the following way: total DNA from Anabaena was digested with various restriction enzymes, fractionated by gel electrophoresis, and blotted onto GeneScreen Plus (DuPont). The blot was hybridized at low stringency (1M NaCl, 57.degree. C.) with a probe consisting of a SstII-PstI fragment containing about 90% of the coding region of the fabG gene from E. coli. This probe identified a 3.1-kb HindIII fragment in the Anabaena digest that contained similar sequences. A mixture of about 3-kb HindIII fragments of Anabaena DNA was purified, then digested with NheI, yielding a HindIII-NheI fragment of 1.6 kb that hybridized with the fabG probe. The 1.6-kb region was purified by gel electrophoresis and cloned into pUC18.
Plasmid minipreps were made from about 160 colonies, of which four were found to contain the 1.6-kb HindIII-NheI fragment that hybridized with the fabG probe. The 1.6-kb Anabaena fragment was then used as probe to screen, at high stringency (1M NaCl, 65.degree. C.), a cosmid library of Anabaena DNA inserts averaging 40 kb in size. Five were found among 1920 tested, all of which contained the same size HindIII and NheI fragments as those identified by the E. coli probe previously. From one of the cosmids, the 3.1-kb HindIII fragment containing the Anabaena fabG gene was subcloned into pUC18 and sequenced using the dideoxy chain termination method. The complete nucleotide sequence of this fragment is shown in FIG. 1 (SEQ ID NO:1 and SEQ ID NO:2).
A similar procedure was used to clone the fabG gene from Synechococcus. In this case, the initial Southern hybridization showed that the desired sequences were contained in part on an 0.8-kb BamHI-PstI fragment. This size fragment was purified in two steps and cloned into the plasmid Bluescript KS. Minipreps of plasmids from 200 colonies revealed two that contained the appropriate fragment of Synechococcus DNA. This fragment was used to probe, at high stringency, a library of Synechococcus inserts in the cosmid vector pWB79. One positive clone was found among 1728 tested. This cosmid contained a 2-kb BamHI and a 3-kb PstI fragment that had previously been identified by the E. coli fabG probe in digests of total Synechococcus DNA. Both fragments were subcloned from the cosmid into Bluescript KS and 2.4 kb, including the coding part of the fabG gene, were sequenced. The complete sequence of the coding region of the Synechococcus fabG gene is shown in FIG. 2 (SEQ ID NO:5 and SEQ ID NO:6).
In another aspect, the present invention provides an isolated and purified polynucleotide of from about 480 to about 40,000 base pairs that encodes a biotin carboxyl carrier protein of a cyanobacterium. That biotin carboxyl carrier protein preferably includes the amino acid residue sequence of FIG. 8 (SEQ ID NO:111 ) or a functional equivalent thereof. A preferred polynucleotide that encodes that polypeptide includes the DNA sequence of SEQ ID NO:110 (FIG. 8).
B. Plants
Another polynucleotide contemplated by the present invention encodes a plant polypeptide having the ability to catalyze the carboxylation of acetyl-CoA. Such a plant polypeptide is preferably a monocotyledonous or a dicotyledonous plant acetyl-CoA carboxylase enzyme.
An exemplary and preferred monocotyledonous plant is wheat, rice, maize, barley, rye, oats or timothy grass. An exemplary and preferred dicotyledonous plant is soybean, rape, sunflower, tobacco, Arabidopsis, petunia, pea, Canola, bean, tomato, potato, lettuce, spinach, alfalfa, cotton or carrot.
A monocotyledonous plant polypeptide is preferably wheat ACC, which ACC includes the amino acid residue sequence of SEQ ID NO:109 (FIG. 6) or a functional equivalent thereof. A preferred polynucleotide that encodes such a polypeptide includes the DNA sequence of SEQ ID NO:108 (FIG. 6).
Amino acid sequences of biotin carboxylase (BC) from Anabaena and Synechococcus show great similarity with amino acid residue sequences from other ACC enzymes as well as with the amino acid residue sequences of other biotin-containing enzymes (See FIG. 3). Based on that homology, the nucleotide sequences shown in FIG. 4 (SEQ ID NO:112 and SEQ ID NO:113) were chosen for the construction of primers for polymerase chain reaction amplification of a corresponding region of the gene for ACC from wheat. Those primers have the nucleotide sequences shown below: ##STR1## where N is A, C, G or T; H is A, C or T; R is A or G; Y is T or C and K is G or T. Primers 1 and 2 comprise a 14-nucleotide specific sequence based on a conserved amino acid sequence and an 8-nucleotide extension at the 5'-end of the primer to provide anchors for rounds of amplification after the first round and to provide convenient restriction sites for analysis and cloning.
cDNA amplification began with a preparation of total polyA-containing mRNA from eight day-old green plants (Triticum aestivum var. Era as described in [Lamppa, et al., 1992]). The first strand of cDNA was synthesized using random hexamers as primers for AMV reverse transcriptase following procedures described in [Haymerle, et al., 1986], with some modifications. Reverse transcriptase was inactivated by heat and low molecular weight material was removed by filtration.
The PCR was initiated by the addition of polymerase at 95.degree. C. Amplification was for 45 cycles, each 1 min at 95.degree., 1 min at 42.degree.-46.degree. and 2 min at 72.degree. C. Both the reactions using Anabaena DNA and the single-stranded wheat cDNA as template yielded about 440 base pair (bp) products. The wheat product was eluted from a gel and reamplified using the same primers. That product, also 440 bp, was cloned into the Invitrogen (San Diego, Calif.) vector pCR1000 using their A/T tail method, and sequenced.
In eukaryotic ACCs, a BCCP domain is located about 300 amino acids away from the end of the BC domain, on the C-terminal side. Therefore, it is possible to amplify the cDNA covering the interval between the BC and BCCP domains using primers from the C-terminal end of the BC domain and the conserved MKM region of the BCCP. The BC primer was based on the wheat cDNA sequence obtained as described above. Those primers, each with 6- or 8-base 5'-extensions, are shown below and in FIG. 5. ##STR2## N, R and Y are as defined above. W is A or T. The BC primer (Primer 3) was based on the wheat cDNA sequence obtained as described above. The MKM primer (primer 4) was first checked by determining whether it would amplify the fabE gene coding BCCP from Anabaena DNA. This PCR was primed at the other end by using a primer based on the N-terminal amino acid residue sequence as determined on protein purified from Anabaena extracts by affinity chromatography. Those primers are shown below and in FIG. 7. ##STR3## H, N, R, T, Y and W are as defined above. M is A or C. This amplification (using the conditions described above) yielded the correct fragment of the Anabaena fabE gene, which was used to identify cosmids that contained the entire fabE gene and flanking DNA. An about 4 kb XbaI fragment containing the gene was cloned into the vector Bluescript KS for sequencing.
Primers 3 and 4 were then used to amplify the intervening sequence in wheat cDNA. Again, the product of the first PCR was eluted and reamplified by another round of PCR, then cloned into the Invitrogen vector pCRII.
The complete 1.1 kb of the amplified DNA was sequenced, shown in FIG. 6, (SEQ ID NO:108); nucleotides 376-1473. The nucleotide sequence of the BC domain is also shown in FIG. 6 (SEQ ID NO:108), nucleotides 1-422. Three clones of the BC domain gave the sequence shown. Four clones of the 1.1-kb fragment differed at several positions, corresponding to three closely related sequences, all of which are indicated in the Figure. Most of the sequence differences are in the third codon position and are silent in terms of the amino acid sequence.
The amino acid sequence of the polypeptide predicted from the cDNA sequence for this entire fragment of wheat cDNA (1473 nucleotides) is compared with the amino acid sequences of other ACC enzymes and related enzymes from various sources in FIG. 3. The most significant identities are with the ACC of rat, chicken and yeast, as shown in the table below. Less extensive similarities are evident with the BC subunits of bacteria and the BC domains of other enzymes such as pyruvate carboxylase of yeast and propionyl CoA carboxylase of rat. The amino acid identities between wheat ACC and other biotin-dependent enzymes, within the BC domain (amino acid residues 312-630 in FIG. 3) are shown below in Table 1.
C. Probes and Primers
In another aspect, DNA sequence information provided by the invention allows for the preparation of relatively short DNA (or RNA) sequences having the ability to specifically hybridize to gene sequences of the selected polynucleotides disclosed herein. In these aspects, nucleic acid probes of an appropriate length are prepared based on a consideration of a selected ACC gene sequence, e.g., a sequence such as that shown in FIGS. 1, 2, 6 or 8 (SEQ ID NO:110 and SEQ ID NO:111). The ability of such nucleic acid probes to specifically hybridize to an ACC gene sequence lend them particular utility in a variety of embodiments. Most importantly, the probes can be used in a variety of assays for detecting the presence of complementary sequences in a given sample.
In certain embodiments, it is advantageous to use oligonucleotide primers. The sequence of such primers is designed using a polynucleotide of the present invention for use in detecting, amplifying or mutating a defined segment of an ACC gene from a cyanobacterium or a plant using PCR technology. Segments of ACC genes from other organisms can also be amplified by PCR using such primers.
To provide certain of the advantages in accordance with the present invention, a preferred nucleic acid sequence employed for hybridization studies or assays includes sequences that are complementary to at least a 10 to 30 or so long nucleotide stretch of an ACC sequence, such as that shown in FIGS. 1, 2, 6 or 8 (SEQ ID NO:110 and SEQ ID NO:111). A size of at least 10 nucleotides in length helps to ensure that the fragment will be of sufficient length to form a duplex molecule that is both stable and selective. Molecules having complementary sequences over stretches greater than 10 bases in length are generally preferred, though, in order to increase stability and selectivity of the hybrid, and thereby improve the quality and degree of specific hybrid molecules obtained. One will generally prefer to design nucleic acid molecules having gene-complementary stretches of 15 to 20 nucleotides, or even longer where desired. Such fragments may be readily prepared by, for example, directly synthesizing the fragment by chemical means, by application of nucleic acid reproduction technology, such as the PCR technology of U.S. Pat. No. 4,603,102, herein incorporated by reference, or by excising selected DNA fragments from recombinant plasmids containing appropriate inserts and suitable restriction sites.
Accordingly, a nucleotide sequence of the invention can be used for its ability to selectively form duplex molecules with complementary stretches of the gene. Depending on the application envisioned, one will desire to employ varying conditions of hybridization to achieve varying degree of selectivity of the probe toward the target sequence. For applications requiring a high degree of selectivity, one will typically desire to employ relatively stringent conditions to form the hybrids, for example, one will select relatively low salt and.backslash.or high temperature conditions, such as provided by 0.02M-0.15M NaCl at temperatures of 50.degree. C. to 70.degree. C. These conditions are particularly selective, and tolerate little, if any, mismatch between the probe and the template or target strand.
Of course, for some applications, for example, where one desires to prepare mutants employing a mutant primer strand hybridized to an underlying template or where one seeks to isolate an ACC coding sequences for related species, functional equivalents, or the like, less stringent hybridization conditions will typically be needed in order to allow formation of the heteroduplex. In these circumstances, one may desire to employ conditions such as 0.15M-0.9M salt, at temperatures ranging from 20.degree. C. to 55.degree. C. Cross-hybridizing species can thereby be readily identified as positively hybridizing signals with respect to control hybridizations. In any case, it is generally appreciated that conditions can be rendered more stringent by the addition of increasing amounts of formamide, which serves to destabilize the hybrid duplex in the same manner as increased temperature. Thus, hybridization conditions can be readily manipulated, and thus will generally be a method of choice depending on the desired results.
In certain embodiments, it is advantageous to employ a polynucleotide of the present invention in combination with an appropriate label for detecting hybrid formation. A wide variety of appropriate labels are known in the art, including radioactive, enzymatic or other ligands, such as avidin/biotin, which are capable of giving a detectable signal.
In general, it is envisioned that a hybridization probe described herein is useful both as a reagent in solution hybridization as well as in embodiments employing a solid phase. In embodiments involving a solid phase, the test DNA (or RNA) is adsorbed or otherwise affixed to a selected matrix or surface. This fixed nucleic acid is then subjected to specific hybridization with selected probes under desired conditions. The selected conditions depend as is well known in the art on the particular circumstances and criteria required (e.g., on the G+C contents, type of target nucleic acid, source of nucleic acid, size of hybridization probe). Following washing of the matrix to remove nonspecifically bound probe molecules, specific hybridization is detected, or even quantified, by means of the label.
D. Expression Vector
The present invention contemplates an expression vector comprising a polynucleotide of the present invention. Thus, in one embodiment an expression vector is an isolated and purified DNA molecule comprising a promoter operatively linked to an coding region that encodes a polypeptide having the ability to catalyze the carboxylation of a biotin carboxyl carrier protein of a cyanobacterium, which coding region is operatively linked to a transcription-terminating region, whereby the promoter drives the transcription of the coding region.
As used herein, the term "operatively linked" means that a promoter is connected to an coding region in such a way that the transcription of that coding region is controlled and regulated by that promoter. Means for operatively linking a promoter to a coding region are well known in the art.
Where an expression vector of the present invention is to be used to transform a cyanobacterium, a promoter is selected that has the ability to drive and regulate expression in cyanobacteria. Promoters that function in bacteria are well known in the art. An exemplary and preferred promoter for the cyanobacterium Anabaena is the glnA gene promoter. An exemplary and preferred promoter for the cyanobacterium Synechococcus is the psbAl gene promoter. Alternatively, the cyanobacterial fabG gene promoters themselves can be used.
Where an expression vector of the present invention is to be used to transform a plant, a promoter is selected that has the ability to drive expression in plants. Promoters that function in plants are also well known in the art. Useful in expressing the polypeptide in plants are promoters that are inducible, viral, synthetic, constitutive as described by Poszkowski et al., EMBO J., 3:2719 (1989) and Odell et al., Nature, 313:810 (1985), and temporally regulated, spatially regulated, and spatiotemporally regulated as given in Chua et al., Science, 244:174-181 (1989).
A promoter is also selected for its ability to direct the transformed plant cell's or transgenic plant's transcriptional activity to the coding region. Structural genes can be driven by a variety of promoters in plant tissues. Promoters can be near-constitutive, such as the CaMV 35S promoter, or tissue specific or developmentally specific promoters affecting dicots or monocots.
Where the promoter is a near-constitutive promoter such as CaMV 35S, increases in polypeptide expression are found in a variety of transformed plant tissues (e.g. callus, leaf, seed and root). Alternatively, the effects of transformation can be directed to specific plant tissues by using plant integrating vectors containing a tissue-specific promoter.
An exemplary tissue-specific promoter is the Lectin promoter, which is specific for seed tissue. The Lectin protein in soybean seeds is encoded by a single gene (Le1) that is only expressed during seed maturation and accounts for about 2 to about 5 percent of total seed mRNA. The Lectin gene and seed-specific promoter have been fully characterized and used to direct seed specific expression in transgenic tobacco plants. See, e.g., Vodkin et al., Cell, 34:1023 (1983)and Lindstrom et al., Developmental Genetics, 11:160 (1990).
An expression vector containing a coding region that encodes a polypeptide of interest is engineered to be under control of the Lectin promoter and that vector is introduced into plants using, for example, a protoplast transformation method. Dhir et al., Plant Cell Reports, 10:97 (1991). The expression of the polypeptide is directed specifically to the seeds of the transgenic plant.
A transgenic plant of the present invention produced from a plant cell transformed with a tissue specific promoter can be crossed with a second transgenic plant developed from a plant cell transformed with a different tissue specific promoter to produce a hybrid transgenic plant that shows the effects of transformation in more than one specific tissue.
Exemplary tissue-specific promoters are corn sucrose synthetase 1 (Yang et al. Proc. Natl. Acad. Sci. U.S.A., 87:4144-48 (1990)), corn alcohol dehydrogenase 1 (Vogel et al., J. Cell Biochem., (supplement 13D, 312) (1989)), corn zein 19 KD gene (storage protein) (Boston et al., Plant Physiol., 83:742-46), corn light harvesting complex (Simpson, Science, 233:34 (1986), corn heat shock protein (O'Dell et al., Nature, 313:810-12 (1985), pea small subunit RuBP Carboxylase (Poulsen et al., Mol. Gen. Genet., 205:193-200 (1986); Cashmore et al., Gen. Eng. of Plants, Plenum Press, New York, 29-38 (1983), Ti plasmid mannopine synthase (Langridge et al., Proc. Natl. Acad. Sci. USA, 86:3219-3223 (1989), Ti plasmid nopaline synthase (Langridge et al., Proc. Natl. Acad. Sci. USA, 86:3219-3223 (1989), petunia chalcone isomerase (Van Tunen et al., EMBO J., 7:1257 (1988), bean glycine rich protein 1 (Keller et al., EMBO J., 8:1309-14 (1989), CaMV 35s transcript (O'Dell et al., Nature, 313:810-12 (1985) and Potato patatin (Wenzler et al., Plant Mol. Biol., 12:41-50 (1989). Preferred promoters are the cauliflower mosaic virus (CaMV 35S) promoter and the S-E9 small subunit RuBP carboxylase promoter.
The choice of which expression vector and ultimately to which promoter a polypeptide coding region is operatively linked depends directly on the functional properties desired, e.g. the location and timing of protein expression, and the host cell to be transformed. These are well known limitations inherent in the art of constructing recombinant DNA molecules. However, a vector useful in practicing the present invention is capable of directing the expression of the polypeptide coding region to which it is operatively linked.
Typical vectors useful for expression of genes in higher plants are well known in the art and include vectors derived from the tumor-inducing (Ti) plasmid of Agrobacterium tumefaciens described by Rogers et al., Meth. in Enzymol., 153:253-277 (1987). However, several other plant integrating vector systems are known to function in plants including pCaMVCN transfer control vector described by Fromm et al., Proc. Natl. Acad. Sci. USA, 82:5824 (1985). Plasmid pCaMVCN (available from Pharmacia, Piscataway, N.J.) includes the cauliflower mosaic virus CaMV 35S promoter.
In preferred embodiments, the vector used to express the polypeptide includes a selection marker that is effective in a plant cell, preferably a drug resistance selection marker. One preferred drug resistance marker is the gene whose expression results in kanamycin resistance; i.e., the chimeric gene containing the nopaline synthase promoter, Tn5 neomycin phosphotransferase II and nopaline synthase 3' nontranslated region described by Rogers et al., in Methods For Plant Molecular Biology, A. Weissbach and H. Weissbach, eds., Academic Press Inc., San Diego, Calif. (1988).
RNA polymerase transcribes a coding DNA sequence through a site where polyadenylation occurs. Typically, DNA sequences located a few hundred base pairs downstream of the polyadenylation site serve to terminate transcription. Those DNA sequences are referred to herein as transcription-termination regions. Those regions are required for efficient polyadenylation of transcribed messenger RNA (mRNA).
Means for preparing expression vectors are well known in the art. Expression (transformation vectors) used to transform plants and methods of making those vectors are described in U.S. Pat. Nos. 4,971,908, 4,940,835, 4,769,061 and 4,757,011, the disclosures of which are incorporated herein by reference. Those vectors can be modified to include a coding sequence in accordance with the present invention.
A variety of methods has been developed to operatively link DNA to vectors via complementary cohesive termini or blunt ends. For instance, complementary homopolymer tracts can be added to the DNA segment to be inserted and to the vector DNA. The vector and DNA segment are then joined by hydrogen bonding between the complementary homopolymeric tails to form recombinant DNA molecules.
A coding region that encodes a polypeptide having the ability to catalyze the carboxylation of a biotin carboxyl carrier protein of a cyanobacterium is preferably a biotin carboxylase enzyme of a cyanobacterium, which enzyme is a subunit of acetyl-CoA carboxylase and participates in the carboxylation of acetyl-CoA. In a preferred embodiment, such a polypeptide has the amino acid residue sequence of FIG. 1 or FIG. 2, or a functional equivalent of those sequences. In accordance with such an embodiment, a coding region comprises the entire DNA sequence of SEQ ID NO:1 (FIG. 1) or the DNA sequence of SEQ ID NO:1 (FIG. 1) from about nucleotide position 1300 to about nucleotide position 2650 or the DNA sequence of SEQ ID NO:5 (FIG. 2).
In another embodiment, an expression vector comprises a coding region of from about 480 to about 40,000 base pairs that encodes a biotin carboxyl carrier protein of a cyanobacterium. That biotin carboxyl carrier protein preferably includes the amino acid residue sequence of FIG. 8 (SEQ ID NO:111) or a functional equivalent thereof. A preferred such coding region includes the DNA sequence of SEQ ID NO:110 (FIG. 8).
In still yet another embodiment, an expression vector comprises a coding region that encodes a plant polypeptide having the ability to catalyze the carboxylation of acetyl-CoA. Such a plant polypeptide is preferably a monocotyledonous or a dicotyledonous plant acetyl-CoA carboxylase enzyme.
A preferred monocotyledonous plant polypeptide encoded by such a coding region is preferably wheat ACC, which ACC includes the amino acid residue sequence of SEQ ID NO:109 (FIG. 6) or a functional equivalent thereof. A preferred coding region includes the DNA sequence of SEQ ID NO:108 (FIG. 6).
III. Polypeptide
The present invention contemplates a polypeptide that defines a whole or a portion of an ACC of a cyanobacterium or a plant. In one embodiment, thus, the present invention provides an isolated polypeptide having the ability to catalyze the carboxylation of a biotin carboxyl carrier protein of a cyanobacterium such as Anabaena or Synechococcus. Preferably, a biotin carboxyl carrier protein includes the amino acid sequence of SEQ ID NO:111 and the polypeptide has FIG. 1 or FIG. 2 (SEQ ID NO:5 and SEQ ID NO:6).
The present invention also contemplates an isolated and purified biotin carboxyl carrier protein of a cyanobacterium such as Anabaena, which protein includes the amino acid residue sequence of SEQ ID NO:111.
In another embodiment, the present invention contemplates an isolated and purified plant polypeptide having a molecular weight of about 220 KD, dimers of which have the ability to catalyze the carboxylation of acetyl-CoA. Such a polypeptide preferably includes the amino acid residue sequence of SEQ ID NO:109.
Modification and changes may be made in the structure of polypeptides of the present invention and still obtain a molecule having like or otherwise desirable characteristics. For example, certain amino acids may be substituted for other amino acids in a protein structure without appreciable loss of interactive binding capacity with structures such as, for example, antigen-binding regions of antibodies or binding sites on substrate molecules. Since it is the interactive capacity and nature of a polypeptide that defines that polypeptide's biological functional activity, certain amino acid sequence substitutions can be made in a polypeptide sequence (or, of course, its underlying DNA coding sequence) and nevertheless obtain a polypeptide with like or even counterveiling properties (e.g., antagonistic v. agonistic).
In making such changes, the hydropathic index of amino acids may be considered. The importance of the hydropathic amino acid index in conferring interactive biologic function on a protein is generally understood in the art (Kyte & Doolittle, J. Mol. Biol., 157:105-132, 1982). It is known that certain amino acids may be substituted for other amino acids having a similar hydropathic index or score and still result in a protein with similar biological activity. Each amino acid has been assigned a hydropathic index on the basis of their hydrophobicity and charge characteristsics, these are: isoleucine (+4.5); valine (+4.2); leucine (+3.8); phenylalanine (+2.8); cysteine/cystine (+2.5); methionine (+1.9); alanine (+1.8); glycine (-0.4); threonine (-0.7); serine (-0.8); tryptophan (-0.9); tyrosine (-1.3); proline (-1.6); histidine (-3.2); glutamate (-3.5); glutamine (-3.5); aspartate (-3.5); asparagine (-3.5); lysine (-3.9); and arginine (-4.5).
It is believed that the relative hydropathic character of the amino acid determines the secondary structure of the resultant polypeptide, which in turn defines the interaction of the polypeptide with other molecules, for example, enzymes, substrates, receptors, antibodies, antigens, and the like. It is known in the art that an amino acid may be substituted by another amino acid having a similar hydropathic index and still obtain a biological functionally equivalent protein. In such changes, the substitution of amino acids whose hydropathic indices are within .+-.2 is preferred, those which are within .+-.1 are particularly preferred, and those within .+-.0.5 are even more particularly preferred.
Substitution of like amino acids can also be made on the basis of hydrophilicity, particularly where the biological functional equivalent protein or peptide thereby created is intended for use in immunological embodiments. U.S. Pat. No. 4,554,101, incorporated herein by reference, states that the greatest local average hydrophilicity of a protein, as governed by the hydrophilicity of its adjacent amino acids, correlates with its immunogenicity and antigenicity, i.e. with a biological property of the protein.
As detailed in U.S. Pat. No. 4,554,101, the following hydrophilicity values have been asssigned to amino acid residues: arginine (+3.0); lysine (+3.0); aspartate (+3.0.+-.1); glutamate (+3.0.+-.1); serine (+0.3); asparagine (+0.2); glutamine (+0.2); glycine (0); proline (-0.5.+-.1); threonine (-0.4); alanine (-0.5); histidine (-0.5); cysteine (-1.0); methionine (-1.3); valine (-1.5); leucine (-1.8); isoleucine (-1.8); tyrosine (-2.3); phenylalanine (-2.5); tryptophan (-3.4). It is understood that an amino acid can be substituted for another having a similar hydrophilicity value and still obtain a biologically equivalent, and in particular, an immunologically equivalent protein. In such changes, the substitution of amino acids whose hydrophilicity values are within .+-.2 is preferred, those which are within .+-.1 are particularly preferred, and those within .+-.0.5 are even more particularly preferred.
As outlined above, amino acid substitutions are generally therefore based on the relative similarity of the amino acid side-chain substituents, for example, their hydrophobicity, hydrophilicity, charge, size, and the like. Exemplary substitutions which take various of the foregoing characteristics into consideration are well known to those of skill in the art and include: arginine and lysine; glutamate and aspartate; serine and threonine; glutamine and asparagine; and valine, leucine and isoleucine.
The present invention thus contemplates functional equivalents of the polypeptides set forth above. A polypeptide of the present invention is prepared by standard techniques well known to those skilled in the art. Such techniques include, but are not limited to, isolation and purification from tissues known to contain that polypeptide and expression from cloned DNA using transformed cells.
IV. Transformed or Transgenic Cells or Plants
A cyanobacterium, a plant cell or a plant transformed with an expression vector of the present invention is also contemplated. A transgenic cyanobacterium, plant cell or plant derived from such a transformed or transgenic cell is also contemplated.
Means for transforming cyanobacteria are well known in the art. Typically, means of transformation are similar to those well known means used to transform other bacteria such as E. coli. Synechococcus can be transformed simply by incubation of log-phase cells with DNA. (Golden, et al., 1987)
The application of brief, high-voltage electric pulses to a variety of mammalian and plant cells leads to the formation of nanometer-sized pores in the plasma membrane. DNA is taken directly into the cell cytoplasm either through these pores or as a consequence of the redistribution of membrane components that accompanies closure of the pores. Electroporation can be extremely efficient and can be used both for transient expression of clones genes and for establishment of cell lines that carry integrated copies of the gene of interest. Electroporation, in contrast to calcium phosphate-mediated transfection and protoplast fusion, frequently gives rise to cell lines that carry one, or at most a few, integrated copies of the foreign DNA.
Methods for DNA transformation of plant cells include Agrobacterium-mediated plant transformation, protoplast transformation, gene transfer into pollen, injection into reproductive organs, injection into immature embryos and particle bombardment. Each of these methods has distinct advantages and disadvantages. Thus, one particular method of introducing genes into a particular plant strain may not necessarily be the most effective for another plant strain, but it is well known which methods are useful for a particular plant strain.
Agrobacterium-mediated transfer is a widely applicable system for introducing genes into plant cells because the DNA can be introduced into whole plant tissues, thereby bypassing the need for regeneration of an intact plant from a protoplast. The use of Agrobacterium-mediated plant integrating vectors to introduce DNA into plant cells is well known in the art. See, for example, the methods described by Fraley et al., Biotechnology, 3:629 (1985) and Rogers et al., Methods in Enzymology, 153:253-277 (1987). Further, the integration of the Ti-DNA is a relatively precise process resulting in few rearrangements. The region of DNA to be transferred is defined by the border sequences, and intervening DNA is usually inserted into the plant genome as described by Spielmann et al., Mol. Gen. Genet., 205:34 (1986) and Jorgensen et al., Mol. Gen. Genet., 207:471 (1987).
Modern Agrobacterium transformation vectors are capable of replication in E. coli as well as Agrobacterium, allowing for convenient manipulations as described by Klee et al., in Plant DNA Infectious Agents, T. Hohn and J. Schell, eds., Springer-Verlag, New York (1985) pp. 179-203.
Moreover, recent technological advances in vectors for Agrobacterium-mediated gene transfer have improved the arrangement of genes and restriction sites in the vectors to facilitate construction of vectors capable of expressing various polypeptide coding genes. The vectors described by Rogers et al., Methods in Enzymology, 153:253 (1987), have convenient multi-linker regions flanked by a promoter and a polyadenylation site for direct expression of inserted polypeptide coding genes and are suitable for present purposes. In addition, Agrobacteria containing both armed and disarmed Ti genes can be used for the transformations. In those plant strains where Agrobacterium-mediated transformation is efficient, it is the method of choice because of the facile and defined nature of the gene transfer.
Agrobacterium-mediated transformation of leaf disks and other tissues such as cotyledons and hypocotyls appears to be limited to plants that Agrobacterium naturally infects. Agrobacterium-mediated transformation is most efficient in dicotyledonous plants. Few monocots appear to be natural hosts for Agrobacterium, although transgenic plants have been produced in asparagus using Agrobacterium vectors as described by Bytebier et al., Proc. Natl. Acad. Sci. USA, 84:5345 (1987). Therefore, commercially important cereal grains such as rice, corn, and wheat must usually be transformed using alternative methods. However, as mentioned above, the transformation of asparagus using Agrobacterium can also be achieved. See, for example, Bytebier, et al., Proc. Natl. Acad. Sci. USA, 84:5345 (1987).
A transgenic plant formed using Agrobacterium transformation methods typically contains a single gene on one chromosome. Such transgenic plants can be referred to as being heterozygous for the added gene. However, inasmuch as use of the word "heterozygous" usually implies the presence of a complementary gene at the same locus of the second chromosome of a pair of chromosomes, and there is no such gene in a plant containing one added gene as here, it is believed that a more accurate name for such a plant is an independent segregant, because the added, exogenous gene segregates independently during mitosis and meiosis.
More preferred is a transgenic plant that is homozygous for the added structural gene; i.e., a transgenic plant that contains two added genes, one gene at the same locus on each chromosome of a chromosome pair. A homozygous transgenic plant can be obtained by sexually mating (selfing) an independent segregant transgenic plant that contains a single added gene, germinating some of the seed produced and analyzing the resulting plants produced for enhanced carboxylase activity relative to a control (native, non-transgenic) or an independent segregant transgenic plant.
It is to be understood that two different transgenic plants can also be mated to produce offspring that contain two independently segregating added, exogenous genes. Selfing of appropriate progeny can produce plants that are homozygous for both added, exogenous genes that encode a polypeptide of interest. Back-crossing to a parental plant and out-crossing with a non-transgenic plant are also contemplated.
Transformation of plant protoplasts can be achieved using methods based on calcium phosphate precipitation, polyethylene glycol treatment, electroporation, and combinations of these treatments. See, for example, Potrykus et al., Mol. Gen. Genet., 199:183 (1985); Lorz et al., Mol. Gen. Genet., 199:178 (1985); Fromm et al., Nature, 319:791 (1986); Uchimiya et al., Mol. Gen. Genet., 204:204 (1986); Callis et al., Genes and Development, 1:1183 (1987); and Marcotte et al., Nature, 335:454 (1988).
Application of these systems to different plant strains depends upon the ability to regenerate that particular plant strain from protoplasts. Illustrative methods for the regeneration of cereals from protoplasts are described in Fujimura et al., Plant Tissue Culture Letters, 2:74 (1985); Toriyama et al., Theor Appl. Genet., 73:16 (1986); Yamada et al., Plant Cell Rep., 4:85 (1986); Abdullah et al., Biotechnology, 4:1087 (1986).
To transform plant strains that cannot be successfully regenerated from protoplasts, other ways to introduce DNA into intact cells or tissues can be utilized. For example, regeneration of cereals from immature embryos or explants can be effected as described by Vasil, Biotechnology, 6:397 (1988). In addition, "particle gun" or high-velocity microprojectile technology can be utilized. (Vasil, 1992)
Using that latter technology, DNA is carried through the cell wall and into the cytoplasm on the surface of small metal particles as described in Klein et al., Nature, 327:70 (1987); Klein et al., Proc. Natl. Acad. Sci. U.S.A., 85:8502 (1988); and McCabe et al., Biotechnology, 6:923 (1988). The metal particles penetrate through several layers of cells and thus allow the transformation of cells within tissue explants.
Metal particles have been used to successfully transform corn cells and to produce fertile, stable transgenic tobacco plants as described by Gordon-Kamm, W. J. et al., The Plant Cell, 2:603-618 (1990); Klein, T. M. et al., Plant Physiol., 91:440-444 (1989); Klein, T. M. et al., Proc. Natl. Acad. Sci. USA, 85:8502-8505 (1988); and Tomes, D. T. et al., Plant Mol. Biol., 14:261-268 (1990). Transformation of tissue explants eliminates the need for passage through a protoplast stage and thus speeds the production of transgenic plants.
Thus, the amount of a gene coding for a polypeptide of interest (i.e., a polypeptide having carboxylation activity) can be increased in monocotyledonous plants such as corn by transforming those plants using particle bombardment methods. Maddock et al., Third International Congress of Plant Molecular Biology, Abstract 372 (1991). By way of example, an expression vector containing an coding region for a dicotyledonous ACC and an appropriate selectable marker is transformed into a suspension of embryonic maize (corn) cells using a particle gun to deliver the DNA coated on microprojectiles. Transgenic plants are regenerated from transformed embryonic calli that express ACC. Particle bombardment has been used to successfully transform wheat (Vasil et al., 1992).
DNA can also be introduced into plants by direct DNA transfer into pollen as described by Zhou et al., Methods in Enzymology, 101:433 (1983); D. Hess, Intern Rev. Cytol., 107:367 (1987); Luo et al., Plant Mol. Biol. Reporter, 6:165 (1988). Expression of polypeptide coding genes can be obtained by injection of the DNA into reproductive organs of a plant as described by Pena et al., Nature, 325:274 (1987). DNA can also be injected directly into the cells of immature embryos and the rehydration of desiccated embryos as described by Neuhaus et al., Theor. Appl. Genet., 75:30 (1987); and Benbrook et al., in Proceedings Bio Expo 1986, Butterworth, Stoneham, Mass., pp. 27-54 (1986).
The development or regeneration of plants from either single plant protoplasts or various explants is well known in the art. See, for example, Methods for Plant Molecular Biology, A. Weissbach and H. Weissbach, eds., Academic Press, Inc., San Diego, Calif. (1988). This regeneration and growth process typically includes the steps of selection of transformed cells, culturing those individualized cells through the usual stages of embryonic development through the rooted plantlet stage. Transgenic embryos and seeds are similarly regenerated. The resulting transgenic rooted shoots are thereafter planted in an appropriate plant growth medium such as soil.
The development or regeneration of plants containing the foreign, exogenous gene that encodes a polypeptide of interest introduced by Agrobacterium from leaf explants can be achieved by methods well known in the art such as described by Horsch et al., Science, 227:1229-1231 (1985). In this procedure, transformants are cultured in the presence of a selection agent and in a medium that induces the regeneration of shoots in the plant strain being transformed as described by Fraley et al., Proc. Natl. Acad. Sci. U.S.A., 80:4803 (1983).
This procedure typically produces shoots within two to four months and those shoots are then transferred to an appropriate root-inducing medium containing the selective agent and an antibiotic to prevent bacterial growth. Shoots that rooted in the presence of the selective agent to form plantlets are then transplanted to soil or other media to allow the production of roots. These procedures vary depending upon the particular plant strain employed, such variations being well known in the art.
Preferably, the regenerated plants are self-pollinated to provide homozygous transgenic plants, as discussed before. Otherwise, pollen obtained from the regenerated plants is crossed to seed-grown plants of agronomically important, preferably inbred lines. Conversely, pollen from plants of those important lines is used to pollinate regenerated plants.
A transgenic plant of the present invention containing a desired polypeptide is cultivated using methods well known to one skilled in the art. Any of the transgenic plants of the present invention can be cultivated to isolate the desired ACC or fatty acids which are the products of the series of reactions of which that catalyzed by ACC is the first.
A transgenic plant of this invention thus has an increased amount of an coding region (e.g. gene) that encodes a polypeptide of interest. A preferred transgenic plant is an independent segregant and can transmit that gene and its activity to its progeny. A more preferred transgenic plant is homozygous for that gene, and transmits that gene to all of its offspring on sexual mating.
Seed from a transgenic plant is grown in the field or greenhouse, and resulting sexually mature transgenic plants are self-pollinated to generate true breeding plants. The progeny from these plants become true breeding lines that are evaluated for, by way of example, herbicide resistance, preferably in the field, under a range of environmental conditions.
The commercial value of a transgenic plant with increased herbicide resistance or with altered fatty acid production is enhanced if many different hybrid combinations are available for sale. The user typically grows more than one kind of hybrid based on such differences as time to maturity, standability or other agronomic traits. Additionally, hybrids adapted to one part of a country are not necessarily adapted to another part because of differences in such traits as maturity, disease and herbicide resistance. Because of this, herbicide resistance is preferably bred into a large number of parental lines so that many hybrid combinations can be produced.
V. Process of Increasing Herbicide Resistance
Herbicides such as aryloxyphenoxypropionates and cyclohexanediones inhibit the growth of monocotyledonous weeds by interfering with fatty acid biosynthesis of herbicide sensitive plants. ACC is the target enzyme for those herbicides. Dicotyledonous plants, other eukaryotic organisms and prokaryotic organisms are resistant to those compounds.
Thus, the resistance of sensitive monocotyledonous plants to herbicides can be increased by providing those plants with ACC that is not sensitive to herbicide inhibition. The present invention therefore provides a process of increasing the herbicide resistance of a monocotyledonous plant comprising transforming the plant with a DNA molecule comprising a promoter operatively linked to a coding region that encodes a herbicide resistant polypeptide having the ability to catalyze the carboxylation of acetyl-CoA, which coding region is operatively linked to a transcription-terminating region, whereby the promoter is capable of driving the transcription of the coding region in a monocotyledonous plant.
Preferably, a herbicide resistant polypeptide, a dicotyledonous plant polypeptide such as an acetyl-CoA carboxylase enzyme from soybean, rape, sunflower, tobacco, Arabidopsis, petunia, Canola, pea, bean, tomato, potato, lettuce, spinach, alfalfa, cotton or carrot, or functional equivalent thereof. A promoter and a transcription-terminating region are preferably the same as set forth above.
Transformed monocotyledonous plants can be identified using herbicide resistance. A process for identifying a transformed monocotyledonous plant cell comprises the steps of:
(a) transforming the monocotyledonous plant cell with a DNA molecule that encodes a dicotyledonous acetyl-CoA carboxylase enzyme; and
(b) determining the resistance of the plant cell to a herbicide and thereby the identification of the transformed monocotyledonous plant cell.
Means for transforming a monocotyledonous plant cell are the same as set forth above.
The resistance of a transformed plant cell to a herbicide is preferably determined by exposing such a cell to an effective herbicidal dose of a preselected herbicide and maintaining that cell for a period of time and under culture conditions sufficient for the herbicide to inhibit ACC, alter fatty acid biosynthesis or retard growth. The effects of the herbicide can be studied by measuring plant cell ACC activity, fatty acid synthesis or growth.
An effective herbicidal dose of a given herbicide is that amount of the herbicide that retards growth or kills plant cells not containing herbicide-resistant ACC or that amount of a herbicide known to inhibit plant growth. Means for determining an effective herbicidal dose of a given herbicide are well known in the art. Preferably, a herbicide used in such a process is an aryloxyphenoxypropionate or cyclohexanedione herbicide.
VI. Process of Altering ACC Activity
Acetyl-CoA carboxylase catalyzes the carboxylation of acetyl-CoA. Thus, the carboxylation of acetyl-CoA in a cyanobacterium or a plant can be altered by, for example, increasing an ACC gene copy number or changing the composition (e.g., nucleotide sequence) of an ACC gene. Changes in ACC gene composition can alter gene expression at either the transcriptional or translational level. Alternatively, changes in gene composition can alter ACC function (e.g., activity, binding) by changing primary, secondary or tertiary structure of the enzyme. By way of example, certain changes in ACC structure are associated with changes in the resistance of that altered ACC to herbicides. The copy number of such a gene can be increased by transforming a cyanobacterium or a plant cell with an appropriate expression vector comprising a DNA molecule that encodes ACC.
In one embodiment, therefore, the present invention contemplates a process of altering the carboxylation of acetyl-CoA in a cell comprising transforming the cell with a DNA molecule comprising a promoter operatively linked to a coding region that encodes a polypeptide having the ability to catalyze the carboxylation of acetyl-CoA, which coding region is operatively linked to a transcription-terminating region, whereby the promoter is capable of driving the transcription of the coding region in the cyanobacterium.
In a preferred embodiment, a cell is a cyanobacterium or a plant cell, a polypeptide is a cyanobacterial ACC or a plant ACC. Exemplary and preferred expression vectors for use in such a process are the same as set forth above.
Where a cyanobacterium is transformed with a plant ACC DNA molecule, that cyanobacterium can be used to identify herbicide resistant mutations in the gene encoding ACC. In accordance with such a use, the present invention provides a process for identifying herbicide resistant variants of a plant acetyl-CoA carboxylase comprising the steps of:
(a) transforming cyanobacteria with a DNA molecule that encodes a monocotyledonous plant acetyl-CoA carboxylase enzyme to form transformed or transfected cyanobacteria;
(b) inactivating cyanobacterial acetyl-CoA carboxylase;
(c) exposing the transformed cyanobacteria to an effective herbicidal amount of a herbicide that inhibits acetyl-CoA carboxylase activity;
(d) identifying transformed cyanobacteria that are resistant to the herbicide; and
(e) characterizing DNA that encodes acetyl-CoA carboxylase from the cyanobacteria of step (d).
Means for transforming cyanobacteria as well as expression vectors used for such transformation are preferably the same as set forth above. In a preferred embodiment, cyanobacteria are transformed or transfected with an expression vector comprising an coding region that encodes wheat ACC.
Cyanobacteria resistant to the herbicide are identified. Identifying comprises growing or culturing transformed cells in the presence of the herbicide and recovering those cells that survive herbicide exposure.
Transformed, herbicide-resistant cells are then grown in culture, collected and total DNA extracted using standard techniques. ACC DNA is isolated, amplified if needed and then characterized by comparing that DNA with DNA from ACC known to be inhibited by that herbicide.
VII. Process for Determining Herbicide Resistance Inheritibility
In yet another aspect, the present invention provides a process for determining the inheritance of plant resistance to herbicides of the aryloxyphenocypropionate or cyclohexanedione class. That process comprises the steps of:
(a) measuring resistance to herbicides of the aryloxyphenocypropionate or cyclohexanedione class in a parental plant line and in progeny of the parental plant line to;
(b) purifying DNA from the parental plant line and the progeny;
(c) digesting the DNA with restriction enzymes to form DNA fragments;
(d) fractionating the fragments on a gel;
(e) transferring the fragments to a filter support;
(f) annealing the fragments with a labelled RFLP probe consisting of a DNA molecule that encodes acetyl-CoA carboxylase or a portion thereof;
(g) detecting the presence of complexes between the fragments and the RFLP probe; and
(h) correlating the herbicide resistance of step (a) with the complexes of step (g) and thereby the inheritance of herbicide resistance.
In a preferred embodiment, the herbicide resistant variant of acetyl-CoA carboxylase is a dicotyledonous plant acetyl-CoA carboxylase enzyme or a portion thereof. In another preferred embodiment, the herbicide resistant variant of acetyl-CoA carboxylase is a mutated monocotyledonous plant acetyl-CoA carboxylase that confers herbicide resistance or a hybrid acetyl-CoA carboxylase comprising a portion of a dicotyledonous plant acetyl-CoA carboxylase, a portion of a dicotyledonous plant acetyl-CoA carboxylase or one or more domains of a cyanobacterial acetyl-CoA carboxylase.
The inheritability of phenotypic traits such as herbicide resistance can be determined using RFLP analysis. Restriction fragment length polymorphisms (RFLPs) are due to sequence differences detectable by lengths of DNA fragments generated by digestion with restriction enzymes and typically revealed by agarose gel electrophoresis. There are large numbers of restriction endonucleases available, characterized by their recognition sequences and source.
Restriction fragment length polymorphism analyses are conducted, for example, by Native Plants Incorporated (NPI). This service is available to the public on a contractual basis. For this analysis, the genetic marker profile of the parental inbred lines is determined. If parental lines are essentially homozygous at all relevant loci (i.e., they should have only one allele at each locus), the diploid genetic marker profile of the hybrid offspring of the inbred parents should be the sum of those parents, e.g., if one parent had the allele A at a particular locus, and the other parent had B, the hybrid AB is by inference.
Probes capable of hybridizing to specific DNA segments under appropriate conditions are prepared using standard techniques well known to those skilled in the art. The probes are labelled with radioactive isotopes or fluorescent dyes for ease of detection. After restriction fragments are separated by size, they are identified by hybridization to the probe. Hybridization with a unique cloned sequence permits the identification of a specific chromosomal region (locus). Because all alleles at a locus are detectable, RFLP's are co-dominant alleles, thereby satisfying a criteria for a genetic marker. They differ from some other types of markers, e.g., from isozymes, in that they reflect the primary DNA sequence, they are not products of transcription or translation. Furthermore, different RFLP profiles result from different arrays of restriction endonucleases.
The foregoing examples illustrate particular embodiments of the present invention. It will be readily apparent to a skilled artisan that changes, modification and alterations can be made to those embodiments without departing from the true scope or spirit of the invention.
EXAMPLE 1
Isolation of Cyanobacterial ACC Polynucleotides
The polynucleotide of SEQ ID NO:1 contains a gene that encodes the enzyme biotin carboxylase (BC) enzyme from the cyanobacterium Anabaena 7120. This gene was cloned from a total DNA extract of Anabaena that was digested with various restriction enzymes, fractionated by gel electrophoresis, and blotted onto GeneScreen Plus (DuPont).
The blot was hybridized at low stringency (1M NaCl, 57.degree. C.) with a probe consisting of a SstII-PstI fragment containing about 90% of the coding region of the fabG gene from E. coli. This probe identified a 3.1-kb HindIII fragment in the Anabaena digest that contained similar sequences. A mixture of about 3-kb HindIII fragments of Anabaena DNA was purified, then digested with NheI, yielding a HindIII-NheI fragment of 1.6 kb that hybridized with the fabG probe. The 1.6-kb region was purified by gel electrophoresis and cloned into pUC18. Plasmid minipreps were made from about 160 colonies, of which four were found to contain the 1.6-kb HindIII-NheI fragment that hybridized with the fabG probe. The 1.6-kb Anabaena fragment was then used as probe to screen, at high stringency (1M NaCl, 65.degree. C.), a cosmid library of Anabaena DNA inserts averaging 40 kb in size. Five were found among 1920 tested, all of which contained the same size HindIII and NheI fragments as those identified by the E. coli probe previously. From one of the cosmids, the 3.1-kb HindIII fragment containing the Anabaena fabG gene was subcloned into pUC18 and sequenced using the dideoxy chain termination method. The complete nucleotide sequence of this fragment is shown in FIG. 1 (SEQ ID NO:1 and SEQ ID NO:2).
A similar procedure was used to clone the fabG gene from Synechococcus. In this case, the initial Southern hybridization showed that the desired sequences were contained in part on an 0.8-kb BamHI-PstI fragment. This size fragment was purified in two steps and cloned into the plasmid Bluescript KS. Minipreps of plasmids from 200 colonies revealed two that contained the appropriate fragment of Synechococcus DNA. This fragment was used to probe, at high stringency, a library of Synechococcus inserts in the cosmid vector pWB79. One positive clone was found among 1728 tested. This cosmid contained a 2-kb BamHI and a 3-kb PstI fragment that had previously been identified by the E. coli fabG probe in digests of total Synechococcus DNA. Both fragments were subcloned from the cosmid into Bluescript KS and 2.4 kb, including the coding part of the fabG gene, were sequenced. The complete sequence of the coding region of the Anacystis fabG gene is shown in FIG. 2 (SEQ ID NO:5 and SEQ ID NO:6).
EXAMPLE 2
Plant ACC
The amino acid sequences of the fabG genes encoding BC from Anabaena and Synechococcus are aligned with sequences of ACC and other biotin-containing enzymes from several sources in FIG. 3. This comparison allows the designation of several areas of significant conservation among all the proteins, indicated by stars in the Figure. Based on this alignment, the sequences shown in FIG. 4 were chosen for the construction of primers for the polymerase chain reaction, in order to amplify the corresponding region of the gene for ACC from wheat. The primers used for this amplification are shown in FIG. 4. Each consists of a 14-nucleotide specific sequence based on the amino acid sequence and an 8-nucleotide extension at the 5'-end of the primer to provide anchors for rounds of amplification after the first round and to provide convenient restriction sites for future analysis and cloning.
cDNA amplification began with a preparation of total polyA-containing mRNA from eight day-old green plants (Triticum aestivum var. Era as described in [Lamppa, et al., 1992]). The first strand of cDNA was synthesized using random hexamers as primers for AMV reverse transcriptase following procedures described in [Haymerle, et al., 1986], with some modifications. Reverse transcriptase was inactivated by incubation at 90.degree. C. and low molecular weight material was removed by filtration through centricon 100. All components of the PCR (from the Cetus/Perkin-Elmer kit) together with the two primers shown in FIG. 4, except the Taq DNA polymerase, were incubated for 3-5 min at 95.degree. C. The PCR was initiated by the addition of polymerase. Conditions were established and optimized using Anabaena DNA as template, in order to provide the best yield and lowest level of non-specific products for amplification of the target BC gene from Anabaena DNA. Amplification was for 45 cycles, each 1 min at 95.degree., 1 min at 42.degree.-46.degree. and 2 min at 72.degree. C. Both the reactions using Anabaena DNA and the single-stranded wheat cDNA as template yielded about 440-bp products. The wheat product was eluted from a gel and reamplified using the same primers. That product, also 440 bp, was cloned into the Invitrogen vector pCR1000 using their A/T tail method, and sequenced. The nucleotide sequence is shown in FIG. 5.
In eukaryotic ACCs, the BCCP domain is located about 300 amino acids away from the end of the BC domain, on the C-terminal side. Therefore, it is possible to amplify the cDNA covering that interval using primers from the C-terminal end of the BC domain and the conserved MKM region of the BCCP. The BC primer was based on the wheat cDNA sequence obtained as described above. These primers, each with 6- or 8-base 5'-extensions, are shown in FIG. 6B.
The MKM primer was first checked by determing whether it would amplify the fabE gene encoding BCCP from Anabaena DNA. This PCR was primed at the other end by using a primer based on the N-terminal amino acid sequence, determined on protein purified from Anabaena extracts by affinity chromatography, shown in FIG. 6A. This amplification (using the conditions described above) worked, yielding the correct fragment of the Anabaena fabE gene, whose complete sequence is shown in FIG. 7.
The PCR-amplified fragment of the Anabaena fabE gene was used to identify cosmids (three detected in a library of 1920) that contain the entire fabE gene and flanking DNA. A 4-kb XbaI fragment containing the gene was cloned into the vector Bluescript KS for sequencing. The two primers shown in FIG. 6 were then used to amplify the intervening sequence in wheat cDNA. Again, the product of the first PCR was eluted and reamplified by another round of PCR, then cloned into the Invitrogen vector pCRII. The complete 1.1 kb of the amplified DNA was sequenced, also shown in FIG. 5.
The foregoing examples illustrate particular embodiments of the present invention. One of ordinary skill in the art will readily appreciate that changes, modifications and alterations to those embodiments can be made without departing from the true scope or spirit of the invention.
REFERENCES
The references listed below and all references cited herein are incorporated herein by reference to the extent that they supplement, explain, provide a background for, or teach methodology, techniques, and/or compositions employed herein.
1. J. R. Knowles. 1989. The mechanism of biotin-dependent enzymes. Annu. Rev. Biochem. 58: 195-221.
Alix, J.-H. 1989. A rapid procedure for cloning genes from I libraries by complementation of E. coli defective mutants: application to the fabE region of the E. coli chromosome. DNA 8: 779-789.
3. Muramatsu, S., and T. Mizuno. 1989. Nucleotide sequence of the fabE gene and flanking regions containing a bent DNA sequence of Escherichia coli. Nucleic Acids Res. 17: 3982.
4. Li, S., and J. E. Cronan. 1992. The gene encoding the biotin carboxylase subunit of Escherichia coli acetyl-CoA carboxylase. J. Biol. Chem. 267: 855.
5. Lopez-Casillas, F., D. H. Bai, X. Luo, I. S. Kong, M. A. Hermodson, and K. H. Kim. 1988. Structure of the coding sequence and primary amino acid sequence of rat Acetyl-coenzyme A carboxylase. Proc. Natl. Acad. Sci. USA 85: 5784-5788.
6. Takai, T., C. Yokoyama, K. Wada, and T. Tanabe. 1988. Primary structure of chicken liver acetyl-coenzyme A carboxylase deduced from cDNA sequence. J. Biol. Chem.: 2651-2657.
6a. W. A. Feel, S. S. Chirala and S. J. Wakil 1992. Cloning of the yeast FAS3 gene and primary structure of yeast acetyl-CoA carboxylase. Proc Natl Acad, Sci USA 89: 4534-4538.
7. J. L. Harwood. 1988. Fatty acid metabolism. Ann. Rev. Physiol. Plant Mol. Biol. 39: 101-138.
8. Egin-Buhler, B., and J. Ebel. 1983. Improved purification and further characterization of ACC from culture cells of parsley. Eur. J. Biochem. 133: 335-339.
9. Wurtele, E. S. and Nikolau, B. J. 1990. Arch. Biochem. Biophys. 278: 179-186.
10. Slabas, A. R. and Hellyer, A. 1985. Plant Sci. 39: 177-182.
11. Samols, D., C. G. Thornton, V. L. Murtif, G. K. Kumar, F. C. Haase, and H. G. Wood. 1988. Evolutionary conservation among biotin enzymes. J. Biol. Chem. 263: 6461-6464.
12. H. K. Lichtenthaler. 1990.Mode of action of herbicides affecting acetyl-CoA carboxylase and fatty acid biosynthesis. Z. Naturforsch. 45c: 521-528.
13. I. Pecker, D. Chamovitz, H. Linden, G. Sandmann and J. Hirschberg. 1992. A single polypeptide catalyzing the conversion of phytoene to z-carotene is transcriptionally regulated during tomato fruit ripening. Proc Natl Acad Sci USA 89: 4962-4666.
14. G. K. Lamppa, G. Morelli and N-H Chua (1985). Structure and developmental regulation of a wheat gene encoding the major chlorophyll a/b-binding polypeptide. Mol. Cell Biol. 5: 1370-1378.
15. H. Haymerle, J. Herz, G. M. Bressan, R. Frank and K. K. Stanley (1986). Efficient construction of cDNA libraries in plasmid expression vectors using an adaptor strategy. Nucl. Acids Res. 14: 8615-8629.
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Claims
What is claimed is:
1. An isolated and purified polynucleotide of from about 1350 to about 4000 base pairs that encodes a polypeptide that is a subunit of acetyl-CoA carboxylase, that possesses the ability to catalyze the carboxylation of a biotin carboxyl carrier protein of a cyanobacterium and hybridizes under low stringency conditions to a nucleotide sequence selected from the group consisting of SEQ ID NO:1 and SEQ ID NO:5.
2. The polynucleotide according to claim 1 wherein said cyanobacterium is Anabaena or Synechococcus.
3. The polynucleotide according to claim 2 wherein said biotin carboxyl carrier protein includes the amino acid residue sequence shown in SEQ ID NO:111.
4. The polynucleotide according to claim 1 wherein said polypeptide has the amino acid residue sequence of SEQ ID NO:3 or SEQ ID NO:6.
5. The polynucleotide according to claim 1 that includes (a) the DNA sequence of SEQ ID NO:1 from about nucleotide position 1300 to about nucleotide position 2650; (b) the DNA sequence of SEQ ID NO:1; or (c) the DNA sequence of SEQ ID NO:5.
6. An isolated and purified polynucleotide of from about 1500 to about 10,000 base pairs that encodes a polypeptide of a monocotyledonous or a dicotyledonous plant which hybridizes under low stringency conditions to the nucleotide sequence SEQ ID NO:108, wherein the polypeptide has the ability to catalyze the carboxylation of acetyl-CoA.
7. The polynucleotide according to claim 6 wherein said monocotyledonous plant is wheat, rice, maize, barley, rye, oats or timothy grass.
8. The polynucleotide according to claim 6 wherein said dicotyledonous plant is soybean, rape, sunflower, tobacco, Arabidopsis, petunia, canola, pea, bean, tomato, potato, lettuce, spinach, carrot, canola, alfalfa, or cotton.
9. The polynucleotide according to claim 6 wherein said polypeptide includes the amino acid residue sequence of SEQ ID NO:109.
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