Wu Jianghong, Xiang Hui, Qi Yunxia, Yang Ding, Wang Xiaojuan, Sun Hailian, Wang Feng, Liu Bin
Inner Mongolia Prataculture Research Center, Chinese Academy of Science, Hohhot, China; Animal Husbandry Institute, Inner Mongolia Academy of Agricultural & Animal Husbandry Sciences, Hohhot, China; Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, China.
Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, China.
PLoS One. 2014 Sep 24;9(9):e108388. doi: 10.1371/journal.pone.0108388. eCollection 2014.
Stimulated by retinoic acid 6 (STRA6) is the receptor for retinol binding protein and is relevant for the transport of retinol to specific sites such as the eye. The adaptive evolution mechanism that vertebrates have occupied nearly every habitat available on earth and adopted various lifestyles associated with different light conditions and visual challenges, as well as their role in development and adaptation is thus far unknown. In this work, we have investigated different aspects of vertebrate STRA6 evolution and used molecular evolutionary analyses to detect evidence of vertebrate adaptation to the lightless habitat. Free-ratio model revealed significant rate shifts immediately after the species divergence. The amino acid sites detected to be under positive selection are within the extracellular loops of STRA6 protein. Branch-site model A test revealed that STRA6 has undergone positive selection in the different phyla of mammalian except for the branch of rodent. The results suggest that interactions between different light environments and host may be driving adaptive change in STRA6 by competition between species. In support of this, we found that altered functional constraints may take place at some amino acid residues after speciation. We suggest that STRA6 has undergone adaptive evolution in different branch of vertebrate relation to habitat environment.
视黄酸刺激蛋白6（STRA6）是视黄醇结合蛋白的受体，与视黄醇向眼部等特定部位的转运有关。脊椎动物占据了地球上几乎所有可用栖息地并采用了与不同光照条件和视觉挑战相关的各种生活方式的适应性进化机制，以及它们在发育和适应中的作用，目前尚不清楚。在这项工作中，我们研究了脊椎动物STRA6进化的不同方面，并使用分子进化分析来检测脊椎动物适应无光栖息地的证据。自由比率模型显示，物种分化后立即出现了显著的速率变化。检测到处于正选择下的氨基酸位点位于STRA6蛋白的细胞外环内。分支位点模型A检验显示，除啮齿动物分支外，STRA6在哺乳动物的不同门中都经历了正选择。结果表明，不同光照环境与宿主之间的相互作用可能通过物种间的竞争推动STRA6的适应性变化。支持这一点的是，我们发现物种形成后某些氨基酸残基可能会发生功能限制的改变。我们认为，STRA6在脊椎动物的不同分支中相对于栖息地环境经历了适应性进化。
