Two critical detoxification enzyme genes, NlCYP301B1 and NlGSTm2 confer pymetrozine resistance in the brown planthopper (BPH), Nilaparvata lugens Stål

The brown planthopper (BPH), Nilaparvata lugens Stål, is a notorious pest that infests rice across Asia. The rapid evolution of chemical pesticide resistance in BPH poses an ongoing threat to agriculture and human health. Currently, pymetrozine has emerged as a viable alternative to imidacloprid for managing N. lugens. The detoxification of insecticides in insects includes three major metabolic gene families: cytochrome P450 monooxygenases (P450s), glutathione S-transferases (GSTs), and carboxylesterases (CarEs). In this study, highly resistant strains of BPH to pymetrozine (BPH-R₄₀: 705-fold) were created from the susceptible BPH strain through continuous multi-selection. The activities of detoxifying enzymes, including P450s, GSTs, and CarEs were measured. Notably, P450s and GSTs exhibited significantly higher activity in the pymetrozine-resistance strain than that of the susceptible BPH strain. Hence, we characterized P450s and GSTs genes in N. lugens and revealed their phylogeny, structure, motif analysis, and chromosome location. Subsequently, the expression profiles of 53 P450s and 11 GSTs genes were quantified, and two crucial detoxifying enzyme genes, NlCYP301B1 and NlGSTm2, were identified as being involved in pymetrozine resistance. Furthermore, RNA interference (RNAi)-mediated silencing of NlCYP301B1 and NlGSTm2 gene expression significantly increased larval mortality of BPH in response to pymetrozine. To our knowledge, enhancing the activity of key detoxification enzymes to resist insecticides represents a widespread and vital defense mechanism in insects.