Engineering Herbicide Tolerance in Transgenic Plants

Abstract

The herbicide glyphosate is a potent inhibitor of the enzyme 5-enolpyruvylshikimate- 3-phosphate (EPSP) synthase in higher plants. A complementary DNA (cDNA) clone encoding EPSP synthase was isolated from a complementary DNA library of a glyphosate-tolerant Petunia hybrida cell line (MP4-G) that overproduces the enzyme. This cell line was shown to overproduce EPSP synthase messenger RNA as a result of a 20-fold amplification of the gene. A chimeric EPSP synthase gene was constructed with the use of the cauliflower mosaic virus 35S promoter to attain high level expression of EPSP synthase and introduced into petunia cells. Transformed petunia cells as well as regenerated transgenic plants were tolerant to glyphosate.

Selection and Characterization of Sethoxydim- Tolerant Maize Tissue Cultures

“…Furthermore, stepwise increases in herbicide concentration were used to select the variants in each case. Elevation of GS and EPSP synthase in the respective PPT-and glyphosate-tolerant variants is due to gene amplification in both cases (8,28). If a mechanism(s) causing increased gene copy number also causes increased ACCase activity, then the mechanism may differ from the stable gene amplification reported in the other plant examples (8,28).…”

“…A glyphosate-tolerant carrot (Daucus carota) cell line exhibited a 50-fold increase in tolerance and a 12-fold increase in EPSP synthase activity compared with the control (21). Alternatively, closer correspondence of EPSP synthase overproduction and glyphosate tolerance level were reported for a glyphosate-tolerant Petunia hybrida cell line (28,30). Donn et al (8) proposed that, in the case of GS, more than one molecule of herbicide binds the enzyme and that overexpressed but enzymatically inactive enzyme may also bind the The major change in ACCase, the target site enzyme of sethoxydim and haloxyfop, observed in the herbicide-tolerant tissue cultures was an increase in the levels of activity due to overproduction of the enzyme.…”

Gene amplification confers glyphosate resistance in Amaranthus palmeri

“…Increased expression of EPSPS as a molecular glyphosate resistance mechanism has been reported to endow relatively low-level glyphosate resistance in laboratory studies (25)(26)(27), but this report concerns a field weed population. The data reported here indicate that an EPSPS gene amplification in glyphosate-resistant A. palmeri from Georgia results in high levels of EPSPS expression and that this mechanism imparts high-level glyphosate resistance.…”

Engineering of Herbicide Resistance in Plants

“…A chimaeric EPSP gene encoding wild-type precursor EPSP under control of the cauliflower mosaic virus (CaMV) 35S promoter was introduced into petunia plants (Shah et al, 1986b). This promoter has been shown to direct high-level expression of foreign genes in transformed plants (Odell, Nagy and Chua, 1985).…”