Understanding how phenotypic differences between males and females arise from the sex-biased expression of nearly identical genomes can reveal important insights into the biology and evolution of a species. Among Anopheles mosquito species, these phenotypic differences include vectorial capacity, as it is only females that blood feed and thus transmit human malaria. Here, we use RNA-seq data from multiple tissues of four vector species spanning the Anopheles phylogeny to explore the genomic and evolutionary properties of sex-biased genes. We find that, in these mosquitoes, in contrast to what has been found in many other organisms, female-biased genes are more rapidly evolving in sequence, expression, and genic turnover than male-biased genes. Our results suggest that this atypical pattern may be due to the combination of sex-specific life history challenges encountered by females, such as blood feeding. Furthermore, female propensity to mate only once in nature in male swarms likely diminishes sexual selection of post-reproductive traits related to sperm competition among males. We also develop a comparative framework to systematically explore tissue- and sex-specific splicing to document its conservation throughout the genus and identify a set of candidate genes for future functional analyses of sex-specific isoform usage. Finally, our data reveal that the deficit of male-biased genes on the X Chromosomes in Anopheles is a conserved feature in this genus and can be directly attributed to chromosome-wide transcriptional regulation that de-masculinizes the X in male reproductive tissues.

了解雄性和雌性之间的表型差异是如何因几乎相同的基因组的性别偏向表达而产生的，可以揭示对物种生物学和进化的重要见解。在按蚊物种中，这些表型差异包括媒介能力，因为只有雌性吸血并传播人类疟疾。在这里，我们使用来自跨越按蚊系统发育的四种载体物种的多个组织的 RNA-seq 数据来探索性别偏向基因的基因组和进化特性。我们发现，在这些蚊子中，与许多其他生物体中发现的情况相反，雌性基因在序列、表达和基因更新方面比雄性基因进化得更快。我们的结果表明，这种非典型模式可能是由于女性遇到的特定性别生活史挑战（例如吸血）的结合所致。此外，在自然界中，雄性群体中雌性只交配一次的倾向可能会减少与雄性之间精子竞争相关的生殖后特征的性选择。我们还开发了一个比较框架来系统地探索组织和性别特异性剪接，以记录其在整个属中的保守性，并确定一组候选基因，用于未来对性别特异性异构体使用的功能分析。最后，我们的数据表明，按蚊X 染色体上雄性偏向基因的缺陷是该属的一个保守特征，可直接归因于全染色体转录调控，该调控使雄性生殖组织中的 X 去男性化。