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

Glutathione S-transferases (GSTs) were reported to participate in insecticides 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 significantly 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 th..., 1. Insects and chemicals
Spodoptera litura populations used in this study were described in Li et al. (2021a). Briefly, GX population of S. litura, kindly provided by Guangxi Tianyuan Biochemistry Corp Ltd, served as a susceptible population. QJ population of S. litura, collected from the field in 2019, served as a resistant population to pyrethroids and organophosphates. Compared with GX population, QJ population showed 3659-, 295- and 207-fold resistance to β-cypermethrin, phoxim and chlorpyrifos, respectively. And the resistance level to fenvalerate and cyhalothrin were higher than 25000- fold (Li et al., 2021b). The insects were reared in the insectary at 26±1℃, 60-70% relative humidity, 14:10 h of light:dark photoperiod, without exposure to insecticides.
Fenvalerate (93.4%, Jiangsu Changlong Chemicals Co., Ltd, China), β-cypermethrin (95.0%, Beijing Huarong Biochemical Co., Ltd, China), cyhalothrin (98.4%, Beijing Huarong Biochemical Co., Ltd, China), phoxim (91.0%, Beijing Huarong..., Excel