Adaptive neofunctionalization of ancestral CYP6SN2vB following duplication contributes to abamectin resistance in Chilo suppressalis Walker

Abamectin serves as a key alternative for managing diamide-resistant Chilo suppressalis . However, resistance to abamectin itself presents a significant challenge to this pest control, and its genetic basis remains poorly understood. In this study, we report an increase in field resistance to abamectin in populations of C. suppressalis and provide evidence for a cytochrome P450-mediated metabolic resistance mechanism, supported by enzyme activity assays and synergist bioassays. Transcriptomic profiling analysis revealed six candidate P450 genes, among which the duplicated gene CYP6SN2 showed a strong correlation with resistance. Variant CYP6SN2vB was highly expressed in detoxification tissues and mainly produced isoforms with a short 3′-UTR. Functional validation in transgenic Drosophila melanogaster confirmed that overexpression of CYP6SN2vB conferred 2.4- and 1.9-fold resistance to abamectin and emamectin benzoate, whereas CYP6SN2vA had no detectable effect. Molecular docking further revealed that CYP6SN2vB could potentially hydroxylate abamectin via interactions near oxygen-binding motifs. In contrast, the inward-folded substrate recognition site 1 region of CYP6SN2vA compresses the ligand-binding cavity, precluding abamectin interaction. These findings suggest neofunctionalization of CYP6SN2vB following duplication and provide valuable insights into the molecular basis of abamectin resistance in C. suppressalis , with implications for resistance management.