Odorant Receptors Mediating Benzaldehyde Detection in Mythimna separata: Functional Identification and Ligand Selectivity

Benzaldehyde (BA) is a ubiquitous aromatic volatile produced by both plants and insects. In Mythimna separata, it also serves as a male-emitted pheromonal signal that mediates male–male competition by antagonizing the pheromone receptor MsepPR3 and disrupting the perception of the female sex pheromone Z11-16:Ald. Whether M. separata also possesses conventional odorant receptors (ORs) that detect BA as an environmental volatile remains unknown. Here, we investigated the peripheral molecular basis of BA detection in M. separata. Electroantennogram (EAG) recordings revealed robust, dose-dependent responses to BA in both female and male adults, demonstrating that the antennal olfactory system readily detects BA. Candidate ORs were selected based on phylogenetic relationships and functional evidence from homologous receptors in other noctuid moths and subsequently characterized using the Xenopus oocyte expression system. Two BA-responsive ORs with distinct ligand profiles were identified. MsepOR42 displayed a highly selective response to BA, whereas MsepOR29 showed broader tuning and responded to BA, benzyl alcohol and 2-phenylethanol. These results establish the peripheral molecular basis of BA detection in M. separata and reveal that this ecologically important volatile is encoded by ORs with contrasting ligand selectivity. Our findings expand the understanding of aromatic volatile coding in moths and identify candidate molecular targets for odor-based pest management.