广谱高效Bt菌株的筛选及其杀虫蛋白基因的克隆

通过杀虫活性测定，获得1株对菜青虫、小菜蛾、二化螟等多种鳞翅目害虫均有较高杀虫活性的高效苏云金芽孢杆菌Bacillus thuringiensis（Bt）菌株，命名为X-2．同时根据Cryl类蛋白N端部分氨基酸序列设计了1对简并引物，以苏云金芽孢杆菌X-2菌株质粒DNA为模板，应用PCR扩增技术得到一大小为3468bp的DNA片段（Cry1Ab X-2）．该基因编码1155个氨基酸，相对分子质量为130780，等电点pI=5．06．序列比较表明该基因与Cry1Ab类基因高度同源（达95％以上），该基因已在GenBank中登录，登录号为AY847289．

Screening of Bacillus thuringiensis strain with broadspectrum and high toxicity and cloning of its insecticidal crystal protein gene

After the determination of insecticidal activity,one Bacillus thuringiensis strain,showing high toxic to Pieris rapae,Plutclla xylostella and Chilo suppressalis,was obtained and named Bt X-2.Degenerate primers were designed based on the N-terminal partial sequence of Cry1 to amplify the corresponding DNA sequence by touchdown PCR.The amplified fragment,with the length of 3 468 bp,encoding(1 155) amino acid with M_r=130 780 and pI=5.06.The amino acid sequence of Cry1Ab X-2 gene showed more than 95% identity to other Cry1Ab,and it was registered in GenBank(Accession No.AY847289).