Opsins are the primary proteins responsible for light detection in animals. Cnidarians (jellyfish, sea anemones, corals) have diverse visual systems that have evolved in parallel with bilaterians (squid, flies, fish) for hundreds of millions of years. Medusozoans (e.g., jellyfish, hydroids) have evolved eyes multiple times, each time independently incorporating distinct opsin orthologs. Anthozoans (e.g., corals, sea anemones,) have diverse light-mediated behaviors and, despite being eyeless, exhibit more extensive opsin duplications than medusozoans. To better understand the evolution of photosensitivity in animals without eyes, we increased anthozoan representation in the phylogeny of animal opsins and investigated the large but poorly characterized opsin family in the sea anemone Nematostella vectensis. We analyzed genomic and transcriptomic data from 16 species of cnidarians to generate a large opsin phylogeny (708 sequences) with the largest sampling of anthozoan sequences to date. We identified 29 opsins from N. vectensis (NvOpsins) with high confidence, using transcriptomic and genomic datasets. We found that lineage-specific opsin duplications are common across Cnidaria, with anthozoan lineages exhibiting among the highest numbers of opsins in animals. To establish putative photosensory function of NvOpsins, we identified canonically conserved protein domains and amino acid sequences essential for opsin function in other animal species. We show high sequence diversity among NvOpsins at sites important for photoreception and transduction, suggesting potentially diverse functions. We further examined the spatiotemporal expression of NvOpsins and found both dynamic expression of opsins during embryonic development and sexually dimorphic opsin expression in adults. These data show that lineage-specific duplication and divergence has led to expansive diversity of opsins in eyeless cnidarians, suggesting opsins from these animals may exhibit novel biochemical functions. The variable expression patterns of opsins in N. vectensis suggest opsin gene duplications allowed for a radiation of unique sensory cell types with tissue- and stage-specific functions. This diffuse network of distinct sensory cell types could be an adaptive solution for varied sensory tasks experienced in distinct life history stages in Anthozoans.

中文翻译：

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Nematostella vectensis 体现了无眼六角珊瑚中视蛋白的异常扩展和多样性

视蛋白是负责动物光检测的主要蛋白质。刺胞动物（水母、海葵、珊瑚）具有多种视觉系统，这些系统与两侧对称动物（乌贼、苍蝇、鱼）并行进化了数亿年。美杜莎动物（例如水母、水螅）多次进化出眼睛，每次都独立地结合不同的视蛋白直系同源物。珊瑚虫（例如珊瑚、海葵）具有多种光介导行为，尽管没有眼睛，但比水母虫表现出更广泛的视蛋白重复。为了更好地了解没有眼睛的动物光敏性的进化，我们增加了动物视蛋白系统发育中的动物代表，并研究了海葵 Nematostella vectensis 中大型但特征不明确的视蛋白家族。我们分析了 16 种刺胞动物的基因组和转录组数据，生成了迄今为止最大的昆虫动物序列样本的大型视蛋白系统发育图（708 个序列）。我们使用转录组和基因组数据集，以高置信度从 N. vectensis (NvOpsins) 中鉴定出 29 种视蛋白。我们发现，谱系特异性视蛋白重复在刺胞动物中很常见，其中珊瑚虫谱系在动物中表现出最高数量的视蛋白。为了建立 NvOpsins 的假定光感应功能，我们鉴定了其他动物物种中视蛋白功能所必需的典型保守蛋白结构域和氨基酸序列。我们在 NvOpsins 中对光接收和转导重要的位点表现出高度的序列多样性，表明潜在的多样化功能。我们进一步检查了 NvOpsins 的时空表达，发现胚胎发育过程中视蛋白的动态表达和成人中两性视蛋白的表达。这些数据表明，谱系特异性的重复和分歧导致了无眼刺胞动物中视蛋白的广泛多样性，表明这些动物的视蛋白可能表现出新的生化功能。N. vectensis 中视蛋白的可变表达模式表明视蛋白基因重复允许具有组织和阶段特异性功能的独特感觉细胞类型的辐射。这种不同感觉细胞类型的扩散网络可能是昆虫动物在不同生活史阶段经历的各种感觉任务的适应性解决方案。