Multiple cytochrome P450s overexpressed in pyrethroid resistant house flies (Musca domestica)

Abstract

Cytochrome P450 monooxygenases-mediated detoxification is a major mechanism of pyrethroid resistance in house flies. Constitutive overexpression of P450 genes is the main cause for this type of insecticide resistance. In this study, three new P450 genes (CYP6A40, CYP6D8 and CYP6G4) over-expressed in a pyrethroid resistance strain (BJD) were identified. Developmental expression analysis showed that CYP6A40 and CYP6D8 were expressed in all life stages, while CYP6G4 was not transcribed in eggs or larvae. Permethrin resistance and expression level of cytochrome P450s in six house fly populations (the BJD strain and five field-derived house fly populations collected across China) were determined. Compared with the susceptible TJS strain, all the six populations exhibited different levels of resistance to permethrin. Piperonyl butoxide (PBO) reduced permethrin resistance level up to 109-fold, indicating that cytochrome P450-mediated detoxification is responsible for pyrethroid resistance in Chinese house flies. Significant overexpression of more than one of the eight P450 genes (CYP6A5v1, CYP6A5v2, CYP6A36, CYP6A40, CYP6D1, CYP6D3, CYP6D8 and CYP6G4) in the six pyrethroid resistant house fly populations was observed. Differential expression patterns of P450s over-represented in the resistance populations suggested evolutionary plasticity of P450-mediated pyrethroid resistance. CYP6G4 and CYP6D1, commonly over-expressed in resistant populations, were hypothesized to be the important P450s contributing to pyrethroid resistance of Chinese house flies.