Integrated transcriptomic and proteomic analysis reveals the molecular mechanisms of Spodoptera litura response to Beauveria bassiana stress

Spodoptera litura is a globally devastating agricultural pest that has developed severe resistance to chemical insecticides, necessitating environmentally sustainable biocontrol alternatives such as the entomopathogenic fungus Beauveria bassiana. However, the molecular mechanisms governing host-pathogen interactions in this system remain poorly understood. Here, we employed an integrated transcriptomic and proteomic approach to elucidate the molecular responses of S. litura larvae to B. bassiana infection across three spore concentrations . Our multi-omics analysis revealed concentration-dependent transcriptional reprogramming, with moderate fungal loadeliciting the most extensive differential gene expression (2,434 DEGs), while proteomic responses remained remarkably consistent across treatments (437 DEPs per group). Functional enrichment analyses identified key defense modules including cuticle remodeling (chitin metabolism, cuticle proteins), detoxification pathways (glutathione S-transferases, cytochrome P450s), ion homeostasis, and protein quality control systems. Notably, we observed pervasive transcript-protein discordance, particularly at moderate concentration where nine immune-relevant genes exhibited strong transcriptional activation but corresponding proteins were predominantly downregulated, indicating dominant post-transcriptional regulation. Hub protein analysis revealed central regulatory nodes (A0A9J7EJ43, A0A9J7EMV7, A0A9J7IJC7) that likely coordinate multi-pathway immune responses. RNAi-mediated silencing of four candidate genes (SlPCP-C1B, SlCht10, SlGST1-1, and SlGST2) significantly enhanced fungal lethality, validating their protective roles. This study provides a comprehensive molecular framework for insect-fungal interactions, highlighting post-transcriptional regulation as a critical layer of immune control and identifying novel molecular targets for enhancing mycoinsecticide efficacy against this destructive pest.