Identification of a new lineage of pheromone receptors in mirid bugs (Heteroptera: Miridae).

Sex pheromones, typically released by females are crucial signals for the reductive biology of insects, primarily detected by sex pheromone receptors (PRs). A clade of PRs in three mirid bugs, Apolygus lucorum, Adelphocoris lineolatus, and Adelphocoris suturalis, has been found to respond to pheromones, (E)-2-hexenyl butyrate (E2HB) and hexyl butyrate (HB), with higher sensitivity to E2HB. In this study, we aimed to identify PRs responsible for the other two pheromone components, HB and (E)-4-oxo-2-hexenal (4-OHE), by using a combination of phylogenetic analyses, sequence similarity analyses, and in vitro functional studies. As a result, five new candidate PRs (AlucOR34, AlinOR9, AlinOR10, AsutOR9, and AsutOR10) positioned outside of the previously known PR clade were identified. All five PRs were found to respond to both E2HB and HB, with some PRs exhibiting a significant and sensitive binding to HB. However, PRs for 4-OHE remains unidentified. Overall, our study suggests that mirid bugs have evolved two distinct lineages of PRs with similar response profiles. This research offers valuable insights into sex pheromone recognition within the peripheral olfactory system and contributes to the identification of PRs in mirid bugs, providing new targets for developing the behavioral regulators for these insects.