Screening Larval Attractants via Functional Characterization of Odorant-Binding Protein 8 in Tobacco Cutworm ( Spodoptera litura )

Insects heavily depend on chemical communication to mediate ecological interactions, where specific compounds trigger distinct behavioral responses shaping their life history traits. Odorant-binding proteins (OBPs) are critical targets for identifying behavior-modulating compounds. Here, we employed a reverse chemical ecology approach to identify potential larval attractants of Spodoptera litura. This study first analyzed the tissue distribution and ligand-binding profile of S. litura OBP8 (SlitOBP8) using quantitative real-time PCR and fluorescence-based competitive binding assays, determined that SlitOBP8 was highly expressed in the antennae of larvae, and preliminarily screened 12 ligands. Subsequently, RNA interference (RNAi), site-directed mutagenesis, and behavioral assays were combined to functionally validate candidate odorants eliciting larval attraction. The results indicated that SlitOBP8 played a significant role in the process of larvae recognizing the 2-heptanone. Our findings deepen understanding of olfactory mechanisms underpinning host plant selection by insect herbivores and provide a foundation for novel behavior-based control strategies against S. litura.