SlCarE054 in Spodoptera litura (Lepidoptera: Noctuidae) showed direct metabolic activity to β-cypermethrin with stereoselectivity

Carboxylesterases (CarEs) is an important detoxification enzyme system in phase I participating in insecticides resistance. In our previous study, SlCarE054, a CarEs gene from lepidoptera class, was screened out to be upregulated in a pyrethroids and organophosphates resistant population. Its overexpression was verified in two field-collected populations of Spodoptera litura (Lepidoptera: Noctuidae) resistant to pyrethroids and organophosphates by qRT-PCR. Spatiotemporal expression results showed that SlCarE054 was highly expressed in the pupae stage and the digestive tissue midgut. To further explore its role in pyrethroids and organophosphates resistance, its metabolism activity to insecticides was determined by UPLC. Its recombinant protein showed significant metabolism activity to cyhalothrin and fenvalerate, but not to phoxim or chlorpyrifos. The metabolic activity of SlCarE054 to beta-cypermethrin showed stereoselectivity, with higher metabolic activity to theta-cypermethrin than the enantiomer alpha-cypermethrin. The metabolite of beta-cypermethrin was identified as 3-phenoxybenzaldehyde. Further modelling and docking analysis indicated that beta-cypermethrin, cyhalothrin and fenvalerate could bind with the catalytic triad of the 3D structure of SlCarE054. The interaction of beta-cypermethrin with SlCarE054 also showed the lowest binding energy. Our work provides evidence that SlCarE054 play roles in beta-cypermethrin resistance in S. litura.