植食性昆虫在与寄主植物的协同进化中，积累了大量参与化学防御的细胞色素P450基因。昆虫P450基因的多样性和功能分化影响昆虫的食性和寄主选择，同样对昆虫杀虫剂抗性的形成具有至关重要的作用。申请人前期研究发现，多食性害虫棉铃虫基因组内一对氨基酸序列相似度达91.8%的旁系同源P450基因-CYP6AE19和CYP6AE20发生了明显的功能分化，在植物次生性化合物以及杀虫剂的代谢能力上有显著的差异。本项目拟首先通过互换CYP6AE19和CYP6AE20有差异的底物识别区域(SRSs)后进行体外功能表达，确定引起功能变化的底物识别区域。之后通过分子模拟以及定点突变技术，预测并验证关键SRS中导致两个P450功能差异的关键氨基酸，从而阐释棉铃虫P450功能分化的分子机理。本项目的成果可望为昆虫的化学防御、抗药性形成以及多食性害虫的适应性进化研究提供重要线索。

Herbivore insects accumulated many cytochrome P450 genes, which involved in chemical defense, during the co-evolution with host plants. The diversification and functional divergence of insect P450 genes affected insects’ feeding habits, host shifts and also involved in the development of pesticide resistance. The results of my previous research showed that two paralogous cytochrome P450 genes, CYP6AE19 and CYP6AE20, in polyphagous Helicoverpa armigera shared 91.8% sequence identity but showed distinct metabolic capabilities to plant defense chemicals and insecticides. In this study, we prepare to identify the key substrate recognition sites (SRSs), which cause the functional variations, by heterologous expression and in vitro metabolism after exchanging the diverged SRSs between CYP6AE19 and CYP6AE20. Then molecular simulation and site-directed mutagenesis will be used to predict and verify the key amino acid(s) in the key SRS(s). We aim to explore the molecular mechanisms of the functional divergence of H. armigera P450s and provide important implications for the study of insect chemical defense, development of insecticide resistance and the adaptive evolution of polyphagous insects.