SlGSTE8 in Spodoptera litura participated in the resistance to phoxim and chlorpyrifos

Abstract Glutathione S ‐transferases (GSTs) were reported to participate in insecticide resistance by metabolic and antioxidant activities. In our previous study, an ε class gene of GSTs, SlGSTe8 in Spodoptera litura, was screened out to be upregulated in a population resistant to pyrethroids and organophosphates. SlGSTe8 was highly expressed in the larvae stage, and the digestive tissue, foregut, midgut and hindgut, while the relative expression level was low in the pupae stage and other tissues. To further explore its role in the resistance to pyrethroids and organophosphates, the metabolic activity to insecticides by its recombinant protein was determined by Ultra Performance Liquid Chromatography, and its antioxidant enzyme activity was evaluated by disc diffusion assay. The recombinant protein showed significant metabolic activity to phoxim and chlorpyrifos, but not to fenvalerate, cyhalothrin or β‐cypermethrin. After incubation, the depletion rate of chlorpyrifos is 85.3%, higher than that of phoxim (17.5%). Also, the inhibition zone around filter discs decreased significantly after exposure to cumene hydroperoxide in recombinant plasmid than vector only, suggesting significant antioxidant activity of SlGSTE8. Further modelling and docking analysis indicated that the 3D structure of SlGSTE8 was well shaped for phoxim and chlorpyrifos, with the binding energy −5.58 and −5.15 kcal/mol, respectively. Our work provides evidence that SlGSTe8 in S. litura plays important roles in phoxim and chlorpyrifos resistance.