Enterococcus mundtii regulates SfCYP6B39 expression to modulate chlorantraniliprole resistance in Spodoptera frugiperda.

Microbiota-mediated adaptation is increasingly recognized as an important driver of insecticide resistance. Here, we demonstrate that gut symbionts promote chlorantraniliprole resistance in Spodoptera frugiperda through transcriptional regulation of host detoxification pathways. Resistant populations exhibited a distinct gut microbial community dominated by Enterococcus mundtii, accompanied by elevated cytochrome P450 (P450) activity and widespread upregulation of detoxification genes. Disruption of the gut microbiota reduced resistance, suppressed P450 activity, and downregulated multiple P450 genes, whereas recolonization with E. mundtii SC1 restored these effects. Functional analyses employing RNA interference and transgenic Drosophila melanogaster identified SfCYP6B39 as a key gene contributing to resistance. Molecular docking and molecular dynamics simulations further revealed that chlorantraniliprole can stably bind to SfCYP6B39. Mechanistically, E. mundtii SC1 promotes SfCYP6B39 overexpression via the transcription factors CncC and BR-C, forming a microbe-host regulatory axis that links symbiont presence to detoxification gene activation. Collectively, these findings demonstrate that gut symbionts enhance insecticide resistance through transcriptional reprogramming of host detoxification networks, providing mechanistic insight and suggesting microbiome-targeted strategies for sustainable pest management.