Characterization and plant expression of glyphosate-tolerant enolpyruvylshikimate phosphate synthase

Abstract BACKGROUND: Glyphosate tolerance is a dominant trait in modern biotech crops. RESULTS: A gene encoding a glyphosate-tolerant EPSP synthase (aroA 1398 ) from bacterial strain ATX1398 was cloned and characterized. The protein is initiated at a GTG translational start codon to produce a protein that provides robust glyphosate resistance in Escherichia coli (Mig) Cast & Chalm. The aroA 1398 protein was expressed and purified from E. coli, and key kinetic values were determined (K i = 161 µM; K m (PEP) = 11.3 µM; k cat = 28.3 s −1 ). The full-length enzyme is 800-fold more resistant to glyphosate than the maize EPSP synthase while retaining high affinity for the substrate phosphoenol pyruvate. To evaluate further the potential of aroA 1398 , transgenic maize events expressing the aroA 1398 protein were generated. T 0 plants were screened for tolerance to glyphosate sprays at 1.3× commercial spray rates, and T 1 plants were selected that completely resisted glyphosate sprays at 1×, 2× and 4× recommended spray rates in field trials. CONCLUSION: These data suggest that aroA 1398 is a suitable candidate for conferring glyphosate tolerance in transgenic crop plants