Battelle Barbara-Anne, Ryan Joseph F, Kempler Karen E, Saraf Spencer R, Marten Catherine E, Warren Wesley C, Minx Patrick J, Montague Michael J, Green Pamela J, Schmidt Skye A, Fulton Lucinda, Patel Nipam H, Protas Meredith E, Wilson Richard K, Porter Megan L
Whitney Laboratory for Marine Bioscience, Departments of Neuroscience and Biology, University of Florida
Whitney Laboratory for Marine Bioscience, Department of Biology, University of Florida.
Genome Biol Evol. 2016 Jun 3;8(5):1571-89. doi: 10.1093/gbe/evw100.
Horseshoe crabs are xiphosuran chelicerates, the sister group to arachnids. As such, they are important for understanding the most recent common ancestor of Euchelicerata and the evolution and diversification of Arthropoda. Limulus polyphemus is the most investigated of the four extant species of horseshoe crabs, and the structure and function of its visual system have long been a major focus of studies critical for understanding the evolution of visual systems in arthropods. Likewise, studies of genes encoding Limulus opsins, the protein component of the visual pigments, are critical for understanding opsin evolution and diversification among chelicerates, where knowledge of opsins is limited, and more broadly among arthropods. In the present study, we sequenced and assembled a high quality nuclear genomic sequence of L. polyphemus and used these data to annotate the full repertoire of Limulus opsins. We conducted a detailed phylogenetic analysis of Limulus opsins, including using gene structure and synteny information to identify relationships among different opsin classes. We used our phylogeny to identify significant genomic events that shaped opsin evolution and therefore the visual system of Limulus We also describe the tissue expression patterns of the 18 opsins identified and show that transcripts encoding a number, including a peropsin, are present throughout the central nervous system. In addition to significantly extending our understanding of photosensitivity in Limulus and providing critical insight into the genomic evolution of horseshoe crab opsins, this work provides a valuable genomic resource for addressing myriad questions related to xiphosuran physiology and arthropod evolution.
鲎是剑尾目的螯肢动物，是蛛形纲动物的姐妹群。因此，它们对于理解真螯肢亚门最近的共同祖先以及节肢动物的进化和多样化非常重要。美洲鲎是现存四种鲎中研究最多的一种，其视觉系统的结构和功能长期以来一直是对于理解节肢动物视觉系统进化至关重要的研究重点。同样，对编码美洲鲎视蛋白（视觉色素的蛋白质成分）的基因进行研究，对于理解螯肢动物（视蛋白知识有限）以及更广泛的节肢动物中视蛋白的进化和多样化至关重要。在本研究中，我们对美洲鲎的高质量核基因组序列进行了测序和组装，并利用这些数据注释了美洲鲎视蛋白的完整序列。我们对美洲鲎视蛋白进行了详细的系统发育分析，包括利用基因结构和共线性信息来确定不同视蛋白类之间的关系。我们利用系统发育来识别塑造视蛋白进化从而影响美洲鲎视觉系统的重要基因组事件。我们还描述了所鉴定的18种视蛋白的组织表达模式，并表明编码多种视蛋白（包括一种视黄醛结合蛋白）的转录本存在于整个中枢神经系统中。除了显著扩展我们对美洲鲎光敏感性的理解并为鲎视蛋白的基因组进化提供关键见解之外，这项工作还为解决与剑尾目生理学和节肢动物进化相关的众多问题提供了宝贵的基因组资源。
