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微粒体细胞色素P450氧化酶介导的解毒代谢增强是棉铃虫Helicoverpa armigera对拟除虫菊酯类杀虫剂产生抗性的主要原因。作者前期的研究表明,CYP9A12和CYP9A14组成型过量表达与棉铃虫YGF品系对拟除虫菊酯的高水平抗性相关,CYP9A12和CYP9A14的功能表达研究结果为其参与对拟除虫菊酯抗性提供了直接证据。本研究通过对棉铃虫CYP9A17v2的克隆、mRNA表达水平和功能表达的研究,以期明确该基因是否参与棉铃虫对拟除虫菊酯的抗性。结果表明:CYP9A17v2与CYP9A12的氨基酸序列具有很高的相似性(94%)。与棉铃虫对照品系(YG)相比,CYP9A17v2在YGF抗性品系末龄幼虫脂肪体中具有10.9倍的组成型过量表达,而在中肠中未发现过量表达。用酿酒酵母Saccharomyces cerevisiae异源表达的CYP9A17v2能够代谢多种拟除虫菊酯(顺式氰戊菊酯、溴氰菊酯和氟氯氰菊酯)。据此认为CYP9A17v2组成型过量表达参与了棉铃虫对拟除虫菊酯的抗性。至此,CYP9A亚家族中已有3个P450基因(CYP9A12,CYP9A14和CYP9A17v2)被证实参与了棉铃虫对拟除虫菊酯的氧化解毒代谢。
Microsomal cytochrome P450 oxidase-mediated detoxification metabolism is the main reason for the resistance of the H. armigera Helicoverpa armigera to pyrethroid insecticides. Previous studies by the authors showed that constitutive overexpression of CYP9A12 and CYP9A14 was associated with high level of resistance to pyrethroids in the H. armigera YGF strain and that the functional expression studies of CYP9A12 and CYP9A14 provided direct evidence of their involvement in pyrethroid resistance . In this study, we cloned CYP9A17v2 from Helicoverpa armigera (CYP9A17v2) and investigated the expression of CYP9A17v2 in Helicoverpa armigera (CYP9A17v2) to find out whether this gene is involved in the resistance of H. armigera to pyrethroids. The results showed that the amino acid sequences of CYP9A17v2 and CYP9A12 had high similarity (94%). CYP9A17v2 had a 10.9-fold constitutive overexpression in the fat body of late-stage larval fat bodies of the YGF-resistant lines compared to the cotton bollworm control line (YG), whereas no overexpression was found in the midgut. CYP9A17v2 heterologously expressed with the Saccharomyces cerevisiae can metabolize various pyrethroids (cis-fenvalerate, deltamethrin and cyfluthrin). Accordingly, it is considered that constitutive overexpression of CYP9A17v2 is involved in the resistance of the cotton bollworm to pyrethroids. Up to now, three P450 genes (CYP9A12, CYP9A14 and CYP9A17v2) have been involved in the oxidative detoxification of pyrethroids in cotton bollworm.