Patent ID: 6852909

Claim:
A process for producing trangenic plants containing selectively destructable pistil- or stigma parts, wherein the plant possesses resistance to PCT as a result of phosphinothricir fixed precisely by the sequence. The protein sequence is defined by the DNA sequence, An ATG codon, which is recognized in bacteria and plants, is used as the translation start codon; the Shine-Dalgarno sequence is underlined. This gene encodes the last step in the biosynthesis of PTT, i.e. the deacetylation of inactive N-acetylphosphinothricin tripeptide to give the active PTT, It is known that the specificity of many enzymes is not restricted to one substrate. Thus, the phosphinothricin N-acetyltransferase which is encoded by the pat gene is actually used in PTT biosynthesis for acetylating desmethyl-PTC and, because of its lack of specificity, can be used for detoxifying PTC. By means of overexpressing the dea gene (using suitable promoters or by cloning onto high-copy vectors), an insufficiently specific N-acetyl-PTT deacetylase can now be employed for activating N-acetylphosphinothricin, Other dea genes can be isolated from E. coli . Thus, it has been found that in E. coli , in contrast to other bacteria (e.g. rhizobias and streptomycetes ), no activity can be detected in the so-called pat assay (dissertation of Inge Broer, University of Bielefeld Faculty of Biology, Expression des Phosphinthricin-N-Acetyltransferase-Gens aus Streptomyces viridochromogenes in Nicotiana tabacum (Expression of the Streptomyces viridochromogenes phosphinothricin N-acetyltransferase gene in Nicotiana tabacum ), pp. 42-43, 1989) after the pat gene has been cloned into suitable expression vectors (Strauch et al., Gene, 63, 65-74, 1988; Wohlleben et al., Gene, 70, 25-37, 1988). In addition, when present in low copy number in E. coli , the pat gene is unable to confer resistance to PTT since the endogenous deacetylase nullifies the effect of the phosphinothricin N-acetyltransferase. Finally, this deacetylase activity can be demonstrated directly by the efficient inhibition of GS activity which occurs after adding N-acetylphosinothricin. The deacetylase converts N-Ac-PTC into PTC, which then inhibits the GS in a known manner, as can be measured in a γ-glutamyltransferase assay (Bender et al., J. Bacteriol. 129, acetyltransferease activity, in addition, is given an N-Ac-PTC or N-Ac-PTT deacetylase gene under the control of a pistil- or stigma specific promoter, and the pistil- or stigma are caused to die by means of suitable, timely treatment with PTC or PTT.