Identification of an odorant receptor responding to sex pheromones in Spodoptera frugiperda extends the novel type-I PR lineage in moths

In moths, pheromone receptors (PRs) are crucial for intraspecific sexual communication between males and females. Moth PRs are considered as an ideal model for studying the evolution of insect PRs, and a large number of PRs have been identified and functionally characterized in different moth species. Moth PRs were initially thought to fall into a single monophyletic clade in the odorant receptor (OR) family, but recent studies have shown that ORs in another lineage also bind type-I sex pheromones, which indicates that type-I PRs have multiple independent origins in the Lepidoptera. In this study, we investigated whether ORs of the pest moth Spodoptera frugiperda belonging to clades closely related to this novel PR lineage may also have the capacity to bind type-I pheromones and serve as male PRs. Among the 7 ORs tested, only 1 (SfruOR23) exhibited a male-biased expression pattern. Importantly, in vitro functional characterization showed that SfruOR23 could bind several type-I sex pheromone compounds with Z-9-tetradecenal (Z9-14:Ald), a minor component found in female sex pheromone glands, as the optimal ligand. In addition, SfruOR23 also showed weak responses to plant volatile organic compounds. Altogether, we characterized an S. frugiperda PR positioned in a lineage closely related to the novel PR clade, indicating that the type-I PR lineage can be extended in moths.

Automated summary

This study investigated whether odorant receptors (ORs) of the pest moth Spodoptera frugiperda have the capacity to bind type-I sex pheromones and serve as male PRs. Only one OR (SfruOR23) showed a male-biased expression pattern and could bind several type-I sex pheromone compounds. In addition, SfruOR23 also showed weak responses to plant volatile organic compounds. These findings suggest a broader distribution of type-I PRs in moths.