Abstract
Glyphosate is a non-selective broad-spectrum herbicide that inhibits 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS, also designated as AroA), a key enzyme in the aromatic amino acid biosynthesis pathway in microorganisms and plants. Previously, we reported that a novel AroA (PpAroA1) from Pseudomonas putida had high tolerance to glyphosate, with little homology to class I or class II glyphosate-tolerant AroA. In this study, the coding sequence of PpAroA1 was optimized for tobacco. For maturation of the enzyme in chloroplast, a chloroplast transit peptide coding sequence was fused in frame with the optimized aroA gene (PparoA1(optimized)) at the 5' end. The PparoA1(optimized) gene was introduced into the tobacco (Nicotiana tabacum L. cv. W38) genome via Agrobacterium-mediated transformation. The transformed explants were first screened in shoot induction medium containing kanamycin. Then glyphosate tolerance was assayed in putative transgenic plants and its T(1) progeny. Our results show that the PpAroA1 from Pseudomonas putida can efficiently confer tobacco plants with high glyphosate tolerance. Transgenic tobacco overexpressing the PparoA1(optimized) gene exhibit high tolerance to glyphosate, which suggest that the novel PpAroA1 is a new and good candidate applied in transgenic crops with glyphosate tolerance in future.