Odorant receptor structures predict the major female sex pheromone component in a moth

Species isolation in insects can be ensured by prezygotic barriers, such as species-specific sex pheromone blends that mediate sexual attraction and mate recognition. Yet, sex pheromone compositions of many species remain poorly characterized outside important agricultural pests, because of the necessity to access live insects for pheromone extraction, the difficulties in identifying the production period, and the precise identification of behaviorally relevant compounds in extracts.

Here, we use an odorant receptor (OR)-guided approach to identify the major female sex pheromone component of the previously unexplored lily moth, Spodoptera picta. Genome analysis identified S. picta orthologs of the pheromone receptors OR5 and OR75, previously characterized in S. litura and S. littoralis. Structural modeling of OR5 and OR75 combined with molecular docking predicted conserved ligand binding to (Z,E)-9,11-14:OAc, which was confirmed by functional assays on the ORs. Gas chromatography-mass spectrometry analyses of female pheromone gland extracts identified this compound as the major pheromone component, and electrophysiological and behavioral assays further demonstrated that it elicits antennal responses and is sufficient to attract males.

Together, these results establish an innovative receptor structure-based strategy for pheromone identification in non-model species, provide insights into the sexual chemical ecology of S. picta, and clarify the evolutionary pathway by which a unique class of pheromone receptors emerged by gene duplication and gained specificity.