Olfactory Molecular Mechanism Study on the Recognition of the Danger Signal 1‑Octen-3-ol in the Parasitic Wasp Baryscapus dioryctriae

The odor-driven behavior of parasitoids critically determines their efficacy as biological control agents. Although host-seeking mechanisms are well studied, little is known about their danger signal detection capacity. Here, we studied the synergistic action of odorant binding proteins (OBPs) and odorant receptors (ORs) while detecting the repellence of 1-octen-3-ol in Baryscapus dioryctriae. BdioOR58 exhibited specific tuning to 1-octen-3-ol, whereas BdioOBP50 demonstrated strong binding. In vitro, BdioOBP50 modulated BdioOR58 sensitivity to 1-octen-3-ol. In situ hybridization confirmed BdioOR58 and BdioOBP50 colocalization within the same olfactory sensory neurons. In vivo RNAi knockdown confirmed that both proteins are essential for olfactory detection of this compound in B. dioryctriae. Molecular docking and mutagenesis identified Thr195/Tyr305 (BdioOR58) and Arg47/Tyr99 (BdioOBP50) as key binding residues for 1-octen-3-ol. These findings elucidate the mechanism of the olfactory-driven repellency of B. dioryctriae to 1-octen-3-ol, advancing our understanding of odor detection and avoidance in parasitoid wasps and supporting natural enemy-based pest management strategies.