Coordinated regulation of glutathione S-transferases confers metabolic flexibility in multi-insecticide-resistant Frankliniella occidentalis (Pergande).
INTRODUCTION: The evolution of multi-insecticide resistance in insect pests threatens global food security. Although glutathione S-transferases (GSTs) are implicated in detoxification, the coordinated mechanism by which specific gene subfamilies interact to confer broad-spectrum resistance remains inadequately characterized. OBJECTIVE: To dissect the functional allocation and cooperation of GST subfamilies in multi-insecticide-resistant strains of Frankliniella occidentalis. METHODS: We integrated comparative genomics (20 GST genes cloned), transcriptomics (qRT-PCR), RNAi-mediated silencing, molecular docking (AutoDock Vina), and in vitro metabolism assays (UPLC-MS/MS) across susceptible and resistant thrips strains. RESULTS: The two resistant strains (NIL-R and FS-R) exhibited moderate to high resistance to five insecticides (chlorfenapyr, emamectin benzoate, spinetoram, spinosad, and thiamethoxam), accompanied by significantly elevated GSTs activity. Phylogenetic analysis indicates that GSTs include 10 conserved delta and 7 diverse sigma members. The sigma subfamily has undergone a marked expansion due to gene duplication. Delta (FoGSTd1, d4, and d9) and sigma (FoGSTs1, s2, and s6) genes were significantly up-regulated in the resistant strains. RNAi showed specialized functional allocation among GSTs: delta GSTs mediated resistance to spinosad and chlorfenapyr, sigma GSTs were responsible for thiamethoxam resistance, and notably, cooperation between these subfamilies contributed to resistance against emamectin benzoate and spinetoram. Molecular docking and in vitro metabolism assays of FoGSTd9 and FoGSTs1 proteins further supported the functional allocation and cooperative roles of GST subfamilies. CONCLUSION: Our results indicate that F. occidentalis may coordinate GST subfamilies to achieve metabolic flexibility in response to multi-insecticide pressure. This survival strategy, mediated by mechanistic functional allocation and cooperative interactions among subfamilies, may contribute to energy conservation and reduced adaptive costs. Disruption of this coordinated mechanism represents a potential approach for overcoming resistance in agricultural pest populations.