Abstract
Insect 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. In this study, we report the molecular mechanism and biological significance that underlie the generation of SDHC in the German cockroach Blattella germanica. Sexually mature females possess more C29 CHCs, especially the contact sex pheromone precursor 3,11-DimeC29. RNA interference (RNAi) screen against the fatty acid elongase family members combined with heterologous expression of the genes in yeast revealed that both BgElo12 and BgElo24 were involved in hydrocarbon (HC) production, but BgElo24 is of wide catalytic activities and is able to provide substrates for BgElo12, and only the female-enriched BgElo12 is responsible for sustaining female-specific HC profile. Repressing BgElo12 masculinized the female CHC profile, decreased contact sex pheromone level, and consequently reduced the sexual attractiveness of female cockroaches. Moreover, the asymmetric expression of BgElo12 between the sexes is modulated by sex differentiation cascade. Specifically, male-specific BgDsx represses the transcription of BgElo12 in males, while BgTra is 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.
Highlights
Sexual dimorphism is prevalent in the animal kingdom
We demonstrated that the fatty acid elongation step is responsible for sexual dimorphism of cuticular hydrocarbon (CHC) in B. germanica, We identified that both BgElo12 and BgElo24 were participated in HC biosynthesis, but only the female-enriched BgElo12 is the core gene that encodes for the elongase involved in generating more femaleenriched HCs, and the asymmetric expression of BgElo12 between the sexes is modulated by sex differentiation genes: BgDsxM represses the expression of BgElo12 in males, while BgTra removes this repression in females (Fig 7)
Because a female-enriched HC serves as a precursor to a female contact sex pheromone, we revealed the prominence of BgElo12 in sexual behavior
Summary
Sexual dimorphism is prevalent in the animal kingdom. Females and males independently evolve some traits that enhance survival and reproduction under the pressure of divergent selection forces, leading to sexual dimorphism of traits such as body size [1]. Generation and biological significance of sexually dimorphic hydrocarbons submitted to NCBI’s GenBank under the accession selection, asymmetric selection on the sexes can result in the evolution of sexually dimornumbers MT925720 and MW380216–MW380238. Phic traits; these traits are subject to both inter- and intrasexual selection [2,3] Generation and biological significance of sexually dimorphic hydrocarbons submitted to NCBI’s GenBank under the accession selection, asymmetric selection on the sexes can result in the evolution of sexually dimornumbers MT925720 and MW380216–MW380238. phic traits; these traits are subject to both inter- and intrasexual selection [2,3]
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