Metabolic resistance to emamectin benzoate mediated by CYP4C175 and its dual regulatory functions in development and reproduction of Megalurothrips usitatus.

BACKGROUND: Cowpea is a vital vegetable crop in tropical regions, but the Megalurothrips usitatus causes severe yield losses. Emamectin benzoate is widely used for control; however, resistance has emerged and the molecular basis remains unclear. RESULTS: This investigation demonstrates through bioassay analysis that field populations exhibit 9.4-fold higher resistance to emamectin benzoate relative to the laboratory susceptible population, accompanied by significantly elevated basal P450 enzyme content. Pharmacological inhibition of P450 activity using piperonyl butoxide (PBO) significantly increased susceptibility to emamectin benzoate, with a synergistic ratio of 6.49. Transcriptomic profiling and quantitative real-time PCR (RT-qPCR) analyses revealed that CYP4C175 expression is significantly upregulated in response to increasing concentrations and exposure time under emamectin benzoate stress(P < 0.05), with maximal expression observed at 24 h post-LC50 treatment. Transgenic Drosophila melanogaster strains engineered to overexpress CYP4C175 demonstrated significantly enhanced emamectin benzoate tolerance, with LC50 values 7.7-fold higher than those of wild-type controls (P < 0.05). Conversely, RNA interference (RNAi)-mediated silencing of CYP4C175 reduced P450 content and increased susceptibility to emamectin benzoate by 2.74-fold in M. usitatus (P < 0.05). Furthermore, CYP4C175 participates in the regulation of ecdysteroid (20E) and juvenile hormone (JH) signaling. Gene silencing significantly reduced hormone titers and pupation rates. CONCLUSION: These findings establish CYP4C175 as the principal functional gene mediating emamectin benzoate metabolic resistance in M. usitatus, while concurrently fulfilling multiple biological functions in growth, development, and reproductive regulation. This research provides fundamental molecular targets for resistance monitoring and the development of sustainable, environmentally responsible management strategies against M. usitatus. © 2026 Society of Chemical Industry.