Modulation of fatty acid elongation sustains sexually dimorphic hydrocarbons and female attractiveness inBlattella germanica(L.)

Abstract

AbstractInsect cuticular hydrocarbons (CHCs) serve as important intersexual signaling chemicals and generally show variation between the sexes, but little is known about the generation of sexually dimorphic hydrocarbons (SDHCs) in insects. Here, we report the molecular mechanism and biological significance that underling the generation of SDHC in the German cockroach,Blattella germanica. Sexually mature females possess more C29 cuticular hydrocarbons (CHCs), especially the contact sex pheromone precursor 3,11-DimeC29. RNAi screen against fatty acid elongase gene family members and combined with heterologous expression revealed that bothBgElo12andBgElo24were involved in HC production, butBgElo24is of wide catalytic activities and is able to provides substrates forBgElo12, and only the female-enrichedBgElo12was responsible for sustaining female-specific HC profile. RepressingBgElo12masculinized the female CHC profile, decreased contact sex pheromone level and consequently reduced the sexual attractiveness of female cockroaches. Moreover, the asymmetric expression ofBgElo12between the sexes is modulated by sex differentiation cascade. Specifically, male-specificBgDsxrepresses the transcription ofBgElo12in males, whileBgTrais able to remove this effect in females. Our study reveals a novel molecular mechanism responsible for the formation of SDHCs, and also provide evidences on shaping of the SDHCs by sexual selection, as females use them to generate high levels of contact sex pheromone.