Novel targets for herbicides and transgenic plants resistant to said herbicides

Abstract

The invention concerns novel enzymes having an arogenate dehydrogenase activity, in particular arogenate dehydrogenase enzymes of plants, and the genes encoding said enzymes. The inventive arogenate dehydrogenase enzymes catalyze the last stage of the metabolic pathway of tyrosine biosynthesis, and constitute, as such, potential targets of herbicides. Hence the invention also concerns a method for identifying herbicide compounds targeting said enzymes, said herbicide compounds preventing tyrosine biosynthesis by being fixed on said enzymes. The invention further concerns transgenic plants tolerant to herbicide compounds targeting an enzyme involved in the tyrosine biosynthesis pathway, in particular an enzyme involved in the transformation of L-tyrosine prephenate, in particular an arogenate dehydrogenase enzyme. Said plants become tolerant by expression in their tissues of a prephenate dehydrogenase enzyme, said enzyme being insensitive to said herbicide compounds and enabling the plant to synthetize tyrosine despite being treated with said herbicide compounds.

1 - 16 . (canceled) 
     
     
         17 . A chimeric gene comprising, functionally linked to one another, at least:
 (a) one promoter which is functional in a host organism;   (b) a polynucleotide encoding an enzyme having arogenate dehydrogenase activity; and   (c) a terminator element which is functional in a host organism.   
     
     
         18 . The chimeric gene as claimed in  claim 17 , wherein the promoter is a constitutive promoter. 
     
     
         19 . The chimeric gene as claimed in  claim 17 , wherein the promoter is an inducible promoter. 
     
     
         20 . The chimeric gene as claimed in  claim 17 , further comprising a signal peptide or a transit peptide which is functional in said host organism. 
     
     
         21 . The chimeric gene as claimed in  claim 17 , wherein the host organism is a microorganism. 
     
     
         22 . The chimeric gene as claimed in  claim 17 , wherein the host organism is a plant cell or a plant. 
     
     
         23 . An expression or transformation vector comprising a chimeric gene as claimed in  claim 17 . 
     
     
         24 . The vector as claimed in  claim 23 , wherein the vector is a plasmid, a phage or a virus. 
     
     
         25 . A host organism transformed with the vector of  claim 23 . 
     
     
         26 . The host organism as claimed in  claim 25 , wherein the host organism is a microorganism. 
     
     
         27 . The host organism as claimed in  claim 26 , wherein the microorganism is a bacterium of the species  Escherichia coli.    
     
     
         28 . The host organism as claimed in  claim 26 , wherein the microorganism is a yeast of the  Saccharomyces, Kluyveromyces  or  Pichia  genus. 
     
     
         29 . The host organism as claimed in  claim 26 , wherein the microorganism is a baculovirus. 
     
     
         30 . A transformed plant cell comprising the chimeric gene as claimed in  claim 17 . 
     
     
         31 . A method for preparing arogenate dehydrogenase enzyme, comprising
 (a) culturing a transformed organism or plant cell as claimed in  claim 25  in a suitable culture medium;   (b) recovering the arogenate dehydrogenase enzyme from the culture medium by centrifugation or by filtration; and   (c) purifying the enzyme recovered in step (b) by passing it through at least one chromatography column.   
     
     
         32 - 36 . (canceled) 
     
     
         37 . A plant tolerant with respect to an herbicidal compound having as a target an enzyme involved in one of the metabolic steps for conversion of prephenate to L-tyrosine, said plant comprises a gene encoding a prephenate dehydrogenase enzyme and expresses said enzyme in its tissues. 
     
     
         38 . The plant as claimed in  claim 37 , wherein the plant is tolerant with respect to an herbicidal compound having as a target an arogenate dehydrogenase enzyme. 
     
     
         39 . (canceled) 
     
     
         40 . The plant as claimed in  claim 37 , wherein the plant is tolerant with respect to an herbicidal compound having as a target a prephenate aminotransferase enzyme. 
     
     
         41 - 43 . (canceled) 
     
     
         44 . The tolerant plant as claimed in  claim 37 , wherein the gene encoding a prephenate dehydrogenase enzyme originates from a bacterium or yeast. 
     
     
         45 . The tolerant plant as claimed in  claim 44 , wherein the gene encoding a prephenate dehydrogenase enzyme originates from a bacterium of the  Bacillus  genus. 
     
     
         46 . The tolerant plant as claimed in  claim 45 , wherein the gene encoding a prephenate dehydrogenase enzyme is represented by the sequence identifier SEQ ID NO: 16. 
     
     
         47 . The tolerant plant as claimed in  claim 44 , wherein the gene encoding a prephenate dehydrogenase enzyme originates from a bacterium of the  Escherichia  genus. 
     
     
         48 . The tolerant plant as claimed in  claim 47 , wherein the gene encoding a prephenate dehydrogenase enzyme is represented by the sequence identifier SEQ ID NO: 18. 
     
     
         49 . The tolerant plant as claimed in  claim 44 , wherein the gene encoding a prephenate dehydrogenase enzyme originates from a bacterium of the  Erwinia  genus. 
     
     
         50 . The tolerant plant as claimed in  claim 49 , wherein the gene encoding a prephenate dehydrogenase enzyme is represented by the sequence identifier SEQ ID NO: 20. 
     
     
         51 . A method for producing plants tolerant with respect to herbicidal compounds having as a target an enzyme involved in one of the metabolic steps for conversion of prephenate to L-tyrosine, comprising transforming a plant with a gene encoding a prephenate dehydrogenase enzyme in such a way that they express it in their tissues. 
     
     
         52 . The method as claimed in  claim 51 , wherein the plant is tolerant with respect to herbicidal compounds having as a target the arogenate dehydrogenase enzyme. 
     
     
         53 . The method as claimed in  claim 51 , wherein the plant is tolerant with respect to herbicidal compounds having as a target the prephenate aminotransferase enzyme. 
     
     
         54 . The method as claimed in  claim 51 , wherein the prephenate dehydrogenase enzyme originates from a yeast. 
     
     
         55 . The method as claimed in  claim 51 , wherein the prephenate dehydrogenase enzyme originates from a fungus. 
     
     
         56 . The method as claimed in  claim 51 , wherein the prephenate dehydrogenase enzyme originates from a bacterium. 
     
     
         57 . The tolerant plant as claimed in  claim 37 , comprising a chimeric gene comprising, functionally linked to one another, at least:
 (a) one promoter which is functional in said plant;   (b) said gene encoding the prephenate dehydrogenase enzyme;   (c) a terminator element which is functional in said plant; and   (d) at least one other gene containing a polynucleotide encoding a protein of interest.