Increased production of detoxification enzymes appears to be the primary route for insecticide resistance in many crop pests. However, the mechanisms employed by resistant insects for overexpression of detoxification genes involved in insecticide resistance remain obscure. We report here that the NR2E nuclear receptor HR83 plays a critical role in chlorpyrifos resistance by regulating the expression of detoxification genes in the brown planthopper (BPH), Nilaparvata lugens. HR83 was highly expressed in the fat body and ovary of adult females in chlorpyrifos-resistant BPHs. Knockdown of HR83 by RNA interference showed no effect on female fecundity, whereas caused a decrease of resistance to chlorpyrifos. This treatment also led to a dramatic reduction in the expression of multiple detoxification genes, including four UDP-glycosyltransferases (UGTs), three cytochrome P450 monooxygenases (P450s) and four carboxylesterases (CarEs). Among these HR83-regulated genes, UGT-1-3, UGT-2B10, CYP6CW1, CYP4CE1, CarE and Esterase E4-1 were over-expressed both in the fat body and ovary of the resistant BPHs. Functional analyses revealed that UGT-2B10, CYP4CE1, CarE and Esterase E4-1 are essential for the resistance of BPH to chlorpyrifos. Generally, this study implicates HR83 in the metabolic detoxification-mediated chlorpyrifos resistance and suggests that the regulation of detoxification genes may be an ancestral function of the NR2E nuclear receptor subfamily.
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