Sex-determination cascade orchestrates male-male pheromone synthesis in the bean bug

Abstract

Volatile pheromones are vital for insect intraspecific communication, yet the genetic basis of homosexual recognition remains elusive. In the bean bug Riptortus pedestris, we show that two previously identified aggregation pheromone components, (E)-2-hexenyl-(Z)-3-hexenoate (E2HZ3H) and (E)-2-hexenyl-(E)-2-hexenoate (E2HE2H), serve as key chemosensory cues for male-male recognition during mate selection. Their biosynthesis is governed by the sex-determination cascade Rpfmd-Rpdsx. The male-specific isoform Rpdsx_M promotes pheromone production in males and induces ectopic synthesis in females upon knockdown of the feminizing switch gene Rpfmd. Knockdown of Rpdsx_M in males abolishes both compounds, prompting wild-type males to court them as if they were females. Metathoracic gland cells act as the production hub. Behaviourally, E2HZ3H or E2HE2H disrupt mating when applied to females: males avoid such females. E2HZ3H reduces female mobility in the presence of the male-derived primary aggregation pheromone tetradecyl isobutyrate (14:iBu), whereas E2HE2H shows no obvious such effect. These differential effects ensure mating accuracy. The discovery of volatile pheromones functioning in male-male recognition and of their synthesis being governed by the sex-determination cascade updates our understanding of mating accuracy in insect chemical communication.