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 dataset. In particular, odorant receptors (ORs) 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 ORs and odorant binding proteins (OBPs) present only in hexapods (insects) and absent from all other arthropod lineages, indicating that they are not universal adaptations to land. Gustatory receptors (GRs) 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 (IRs) across the Arthropoda. All antennal IRs 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.

化学感应相关基因（Chemosensory-related Gene, CRG）家族在昆虫中已被广泛研究，但整个节肢动物门（Arthropoda）内该家族的演化历史却长期未得到充分探索。本研究借助更为全面的数据集，针对CRG家族演化的现有假说与既往结论展开系统性探讨。具体而言，学界曾提出假说：嗅觉受体（odorant receptors, ORs）在昆虫（六足动物，hexapods）登陆陆地的过程中发生了扩增，但这类受体与其他泛甲壳类演化支，以及其他节肢动物亚门中独立陆地定居事件的关联仍不明确。本研究同时对“节肢动物中哪一类CRG家族最为古老”这一科学假说进行了验证。据此，我们重构了CRG的系统发育树，涵盖来自全新节肢动物基因组与转录组的CRG序列，并绘制了CRG在节肢动物各演化支中的获得与丢失图谱。本研究纳入了甲壳类动物，尤其是桡足类（copepods）——它们隶属于泛甲壳动物亚门，但处于六足类/鳃足类演化支之外——从而大幅提升了分析的可靠性与全面性。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进行了精准注释。研究发现，嗅觉受体（ORs）与气味结合蛋白（odorant binding proteins, OBPs）仅存在于六足动物（昆虫）体内，在所有其他节肢动物演化支中均未检出，这表明二者并非适应陆地环境的通用演化策略。味觉受体（gustatory receptors, GRs）或许是CRG家族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）。我们还明确并验证了触角离子型受体（antennal ionotropic receptors, IRs）在节肢动物中的完整演化历史。Eurytemora affinis体内的所有触角IRs在雄性个体中的表达量均显著高于雌性，这提示这类受体与雄性的配偶识别行为存在紧密关联。本研究是迄今为止针对最大且物种多样性最高的后生动物门类——节肢动物门——所开展的最为全面的CRG家族演化比较分析。