Adaptive Evolution of cry Genes in Bacillus thuringiensis:Implications for Their Specificity Determination  

作　　者：Jin-Yu Wu Fang-Qing Zhao Jie Bai Gang Deng Song Qin Qi-Yu Bao 

机构地区：[1]Institute of Biomedical Informatics, Wenzhou Medical College, Wenzhou 325000, China [2]Insititute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China.

出　　处：《Genomics, Proteomics & Bioinformatics》2007年第2期102-110,共9页基因组蛋白质组与生物信息学报（英文版）

基　　金：This work was supported by the National Natural Science Foundation of China(No.30571009).

摘　　要：The cry gene family, produced during the late exponential phase of growth in Bacillus thuringiensis, is a large, still-growing family of homologous genes, in which each gene encodes a protein with strong specific activity against only one or a few insect species. Extensive studies are mostly focusing on the structural and functional relationships of Cry proteins, and have revealed several residues or domains that are important for the target recognition and receptor attachment. In this study, we have employed a maximum likelihood method to detect evidence of adaptive evolution in Cry proteins, and have identified 24 positively selected residues, which are all located in Domain Ⅱ or Ⅲ. Combined with known data from mutagenesis studies, the majority of these residues, at the molecular level, contribute much to the insect specificity determination. We postulate that the potential pressures driving the diversification of Cry proteins may be in an attempt to adapt for the ＂arm race＂ between δ-endotoxins and the targeted insects, or to enlarge their target spectra, hence result in the functional divergence. The sites identified to be under positive selection would provide targets for further structural and functional analyses on Cry proteins.The cry gene family, produced during the late exponential phase of growth in Bacillus thuringiensis, is a large, still-growing family of homologous genes, in which each gene encodes a protein with strong specific activity against only one or a few insect species. Extensive studies are mostly focusing on the structural and functional relationships of Cry proteins, and have revealed several residues or domains that are important for the target recognition and receptor attachment. In this study, we have employed a maximum likelihood method to detect evidence of adaptive evolution in Cry proteins, and have identified 24 positively selected residues, which are all located in Domain Ⅱ or Ⅲ. Combined with known data from mutagenesis studies, the majority of these residues, at the molecular level, contribute much to the insect specificity determination. We postulate that the potential pressures driving the diversification of Cry proteins may be in an attempt to adapt for the ＂arm race＂ between δ-endotoxins and the targeted insects, or to enlarge their target spectra, hence result in the functional divergence. The sites identified to be under positive selection would provide targets for further structural and functional analyses on Cry proteins.

关 键 词：adaptive evolution Bacillus thuringiensis Cry protein maximum likelihood method 

分 类 号：Q949.3[生物学—植物学]