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Construction of modified Bacillus thuringiensis cry1AC genes based on cry1-5 genes through multi site-directed mutagenesis
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- URLhttps://db.koreascholar.com/Article/Detail/290803
Bt crystal proteins, encoded by cry genes, are a group of insecticidal proteins unique in the Gram-positive and spore-forming bacterium, Bacillus thuringiensis. These cry genes are widely applied as one of the most successful candidates for constructing transgenic crops resistant to pest insects. In our previous report, we found Cry1-5 had high insecticidal activity against Spodoptera larvae although its amino acid sequences showed high similarity (95.6%) to those of Cry1Ac which had low activity. In comparison with Cry1Ac, Cry1-5 had 12 different residues on domain I and II. In order to convert these residues to Cry1-5 randomly, 10 mutagenic primers were designed. Through multi site-directed mutagenesis, we mutated the modified cry1Ac gene by plant codon usage in pOBI-Modcry1Ac based on cry1-5 and constructed 63 mutant cry genes. Among them, 10 mutant cry genes on domain II were selected and their recombinant proteins were expressed by baculovirus expression system. From bioassay results to P. xylostella and S. exigua, we found some mutants have high insecticidal activities to be applicable to transgenic crops.
