Functional characterization of CYP6AE subfamily P450s associated with pyrethroid detoxification in Spodoptera litura

The common cutworm, Spodoptera litura, has developed with varying degrees of resistance to most commonly used insecticides. Cytochrome P450 monooxygenases (P450s) with broad substrate specificities have been frequently reported to be involved in insecticide detoxification, but the underlying mechanisms remain obscure. Herein, seven CYP6AE subfamily P450s which possess six classical substrate recognition sites and several conserved catalytic motifs were identified from the genome of S. litura. Spatiotemporal expression profiles showed that these CYP6AE subfamily members were predominantly expressed in the larval midgut. Among them, CYP6AE43 and CYP6AE48 were significantly induced by three pyrethroids including β-cypermethrin, λ-cyhalothrin and fenvalerate. Knockdown of CYP6AE43 or CYP6AE48 by RNA interference dramatically increased the larval susceptibility to the pyrethroids. When silencing them simultaneously, the larval susceptibility to pyrethroids was higher than when silencing them individually, indicating a cooperative relationship between these two P450s in pyrethroid detoxification. Homology modeling and molecular docking analyses showed that these three pyrethroids could stably bind to CYP6AE43 and CYP6AE48, with the binding free energies from -37.58 to -84.24 kcal mol-1. These results indicate that induction of CYP6AE43 and CYP6AE48 contributes to pyrethroid detoxification and promotes the development of resistance to pyrethroids in S. litura.