Data from: Evolutionary history of chemosensory-related gene families across the Arthropoda

Chemosensory-related gene (CRG) families have been studied extensively in insects, but their evolutionary history across the Arthropoda had remained relatively unexplored. Here, we address current hypotheses and prior conclusions on CRG family evolution using a more comprehensive data set. In particular, odorant receptors were hypothesized to have proliferated during terrestrial colonization by insects (hexapods), but their association with other pancrustacean clades and with independent terrestrial colonizations in other arthropod subphyla have been unclear. We also examine hypotheses on which arthropod CRG family is most ancient. Thus, we reconstructed phylogenies of CRGs, including those from new arthropod genomes and transcriptomes, and mapped CRG gains and losses across arthropod lineages. Our analysis was strengthened by including crustaceans, especially copepods, which reside outside the hexapod/branchiopod clade within the subphylum Pancrustacea. We generated the first high-resolution genome sequence of the copepod Eurytemora affinis and annotated its CRGs. We found odorant receptors and odorant binding proteins present only in hexapods (insects) and absent from all other arthropod lineages, indicating that they are not universal adaptations to land. Gustatory receptors likely represent the oldest chemosensory receptors among CRGs, dating back to the Placozoa. We also clarified and confirmed the evolutionary history of antennal ionotropic receptors across the Arthropoda. All antennal ionotropic receptors in E. affinis were expressed more highly in males than in females, suggestive of an association with male mate-recognition behavior. This study is the most comprehensive comparative analysis to date of CRG family evolution across the largest and most speciose metazoan phylum Arthropoda.

与化学感应相关的基因（Chemosensory-related gene, CRG）家族在昆虫中已被广泛研究，但整个节肢动物门的进化历程却相对未被充分探索。本研究借助更为全面的数据集，对当前关于CRG家族进化的假说与既有结论展开验证。其中，有假说认为气味受体（odorant receptors）在昆虫（六足亚门，hexapods）登陆陆地的过程中发生了扩增，但它们与其他泛甲壳类（pancrustacean）支系以及节肢动物其他亚门中独立陆地殖民事件的关联仍不明确。我们同时也探究了哪一类节肢动物CRG家族最为古老的相关假说。为此，我们重构了CRG的系统发育树，涵盖了来自新测序节肢动物基因组与转录组的CRG，并绘制了CRG在各节肢动物支系中的获得与丢失情况。本分析纳入了甲壳类动物——尤其是桡足类——从而得到强化，这类生物隶属于泛甲壳动物亚门，但并不属于六足亚门/鳃足类支系。我们首次完成了桡足类物种*Eurytemora affinis*的高分辨率基因组测序，并对其CRG进行了注释。我们发现，气味受体与气味结合蛋白（odorant binding proteins）仅存在于六足亚门（昆虫）中，在所有其他节肢动物支系中均缺失，这表明它们并非适应陆地环境的通用机制。味觉受体（gustatory receptors）或许是CRG中最为古老的化学感应受体，其起源可追溯至扁盘动物门（Placozoa）。我们还阐明并证实了触角离子型受体（antennal ionotropic receptors）在节肢动物中的进化历程。*Eurytemora affinis*体内的所有触角离子型受体在雄性个体中的表达量均高于雌性，这提示其与雄性配偶识别行为存在关联。本研究是迄今为止针对最大且物种最为丰富的后生动物门——节肢动物门——所开展的最为全面的CRG家族进化比较分析。