A Pheromone Antagonist Regulates Optimal Mating Time in the Moth Helicoverpa armigera.

Many insect species use multi-component sex pheromones to discriminate among potential mating partners [1-5]. In moths, pheromone blends tend to be dominated by one or two major components, but behavioral responses are frequently optimized by the inclusion of less abundant minor components [6]. An increasing number of studies have shown that female insects use these chemicals to convey their mating availability to males, who can assess the maturity of females and thus decide when to mate [7, 8]. However, little is known about the biological mechanisms that enable males to assess female reproductive status. In this study, we found that females of Helicoverpa armigera avoid nonoptimal mating by inhibiting males with pheromone antagonist cis-11-Hexadecenol (Z11-16:OH). We also show that this antagonist-mediated optimization of mating time ensures maximum fecundity. To further investigate molecular aspects of this phenomenon, we used the CRISPR/Cas9 system to knock out odorant receptor 16 (OR16), the only pheromone receptor tuned to Z11-16:OH. In mutant males, electrophysiological and behavioral responses to Z11-16:OH were abolished. Inability to detect Z11-16:OH prompted the males to mate with immature females, which resulted in significantly reduced viability of eggs. In conclusion, our study demonstrates that the sensitivity of OR16 to Z11-16:OH regulates optimal mating time and thus ensures maximum fecundity. These results may suggest novel strategies to disrupt pest insect mating.