Over-expression of the Gr5(aroA) gene from glyphosate-contaminated soil confers high tolerance to glyphosate in tobacco

Herbicide resistance is the most widely used transgenic crop trait for broad-spectrum control of weeds. Here we report a novel 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene (Gr5 (aroA) ) isolated from glyphosate-contaminated soil. The full Gr5 (aroA) gene was 1,819 bp and contained a 1,341-bp open reading frame encoding a 47-kDa protein. Phylogenetic analysis showed that Gr5(aroA) is a class I EPSPS even though most such enzymes are naturally sensitive to glyphosate. Interestingly, Gr5(aroA) protein contained highly conserved PEP and S3P binding residues (Glu-351) and several motifs insensitive to glyphosate. Transgenic Gr5 (aroA) plants (T (0)) grew normally and produced seeds which we treated with a high-glyphosate solution (4x recommended spray). Analysis of the T (1) progenies showed that Gr5 (aroA) was inherited at a Mendelian 3:1 segregation ratios and that glyphosate tolerance in T (1) plants was unchanged. Our results show the Gr5 (aroA) gene to be a promising candidate for the development of commercial transgenic crops with high glyphosate tolerance.