Genetic and genomic architecture of species-specific cuticular hydrocarbon variation in parasitoid wasps

Cuticular hydrocarbons (CHCs) serve two fundamental functions in insects: protection against desiccation and chemical signaling. How the interaction of genes shapes CHC profiles, which are essential for insect survival, adaptation, and reproductive success, is still poorly understood. Here we investigate the genetic and genomic basis of CHC biosynthesis and variation in parasitoid wasps of the genus Nasonia. We mapped 91 quantitative trait loci (QTL) explaining variation of a total of 43 CHCs in F2 hybrid males from interspecific crosses between three Nasonia species. To identify candidate genes, we localized orthologs of CHC biosynthesis-related genes in the Nasonia genomes. We discovered multiple genomic regions where the location of QTL coincides with the location of CHC biosynthesis-related candidate genes. Most conspicuously, on a region on chromosome 1 close to the centromere, multiple CHC biosynthesis-related candidate genes co-localize with several QTL explaining variation in methyl-branched alkanes. The genetic underpinnings behind this compound class are not well understood so far, despite their high potential for encoding chemical information as well as their prevalence in hymenopteran CHC profiles. Our study considerably extends our knowledge on the genetic architecture governing this fundamental compound class, establishing a model for methyl-branched alkane genetics in the Hymenoptera in general.

表皮碳氢化合物（Cuticular hydrocarbons, CHCs）在昆虫体内发挥两项核心功能：抵御干燥与参与化学信号传导。目前学界对于基因互作如何塑造表皮碳氢化合物谱，而这类谱型对昆虫的生存、适应以及繁殖成功至关重要，仍知之甚少。本研究针对纳森小蜂属（Nasonia）寄生蜂的表皮碳氢化合物生物合成与变异的遗传及基因组基础展开探究。我们在3个纳森小蜂属物种间的种间杂交获得的F₂杂合雄蜂中，定位了91个可解释共计43种表皮碳氢化合物变异的数量性状基因座（quantitative trait loci, QTL）。为筛选候选基因，我们在纳森小蜂属的基因组中定位了与表皮碳氢化合物生物合成相关基因的直系同源基因。本研究发现多个基因组区域中，QTL的定位区域与表皮碳氢化合物生物合成相关候选基因的位置重合。最为显著的是，在1号染色体靠近着丝粒的区域，多个表皮碳氢化合物生物合成相关候选基因与数个可解释甲基支链烷烃（methyl-branched alkanes）变异的QTL共定位。尽管甲基支链烷烃这类化合物在编码化学信息方面具有极高潜力，且在膜翅目昆虫的表皮碳氢化合物谱中广泛存在，但目前学界对其背后的遗传基础仍了解不足。本研究极大拓展了我们对调控这类核心化合物的遗传结构的认知，同时为膜翅目昆虫的甲基支链烷烃遗传研究建立了通用模型。