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 (PparoA1optimized) at the 5′ end. The PparoA1optimized 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 T1 progeny. Our results show that the PpAroA1 from Pseudomonas putida can efficiently confer tobacco plants with high glyphosate tolerance. Transgenic tobacco overexpressing the PparoA1optimized 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.
Highlights
Genetically modified (GM) crops are cultivated on the fields of 148 million hectares around the world [1]
Pseudomonas putida 4G-1 with high tolerance to glyphosate, which showed little homology to class I as well as class II AroAs
The result showed that PparoA1 has a codon adaptation index (CAI) value (,0.7) in tobacco (Nicotiana tabacum), suggesting that it could be applied directly for generating transgenic plants in it
Summary
Genetically modified (GM) crops are cultivated on the fields of 148 million hectares around the world [1]. Twenty-nine countries have approved planting of biotech crops and another thirty countries have approved import of biotech products for food and feed use. About 61% of GM crops are engineered for herbicide resistance (HR), including soybean, maize, canola, cotton, sugarbeet and alfalfa [1]. Glyphosate-resistant (GR) trait has been dominant in HR technology planted [2]. Since 1996, this trait has been rapidly adapted in soybean, cotton, maize and canola. GR crops marketed as Roundup Ready occupy the greatest acreage [2]
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