Adaptive evolution and functional constraint at TLR4 during the secondary aquatic adaptation and diversification of cetaceans.
Adaptive evolution and functional constraint at TLR4 during the secondary aquatic adaptation and diversification of cetaceans.
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鲸目动物二次水生适应和多样化过程中 TLR4 的适应性进化和功能限制
DOI：
10.1186/1471-2148-12-39
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发表时间：
2012-03-24
影响因子：
3.4
通讯作者：
Yang G
中科院分区：
文献类型：
--
作者：
Shen T;Xu S;Wang X;Yu W;Zhou K;Yang G
鲸类（鲸、海豚和鼠海豚）是一组适应性海洋哺乳动物，具有从陆地向完全水生栖息地过渡的神秘历史，并且在世界各地的沃茨中快速辐射。在整个进化过程中，病原体应激反应蛋白必须面对来自环境病原体在完全不同的生态位鲸类动物所占据的巨大变化的挑战。因此，鲸类可能是研究脊椎动物先天免疫系统进化过程及其相关驱动机制的最理想候选类群之一，如Toll样受体（TLR），位于宿主与微生物环境的直接界面，在识别微生物特异性保守组分的第一线起作用，并将其迅速转化为防御反应。ResultsWe使用TLR 4作为一个例子，以测试是否这个传统上被认为是模式识别受体分子驱动的正选择在鲸类动物的进化史。总体而言，谱系特异性选择测试显示，沿着沿着大多数（33个中的30个）被检查的鲸偶蹄目动物谱系的dN/dS（ω）值小于1，表明功能限制的共同效应。然而，一些特定的密码子发生了根本性的变化，落在与脂多糖（LPS）相互作用的残基附近，并显示独立谱系之间的平行进化，表明TLR 4正选择。特别是，在两个时期，TLR 4上的适应性进化的强烈信号被确定，一个时期对应于鲸类的陆生祖先从陆地到半水生的早期进化过渡（以通向鲸鱼+河马的分支为代表）和从半水生到全水生（以通往鲸类的祖先分支为代表）栖息地，另一个是海洋海豚的快速多样化和辐射.ConclusionsThis是迄今为止第一个研究的特点TLR基因在鲸目动物。我们的数据表明，鲸类TLR 4经历了适应性进化的净化选择的背景下，在海洋中的次级水生适应和快速多样化的反应。这些结果表明，不同环境中的病原微生物是促使鲸类TLR 4发生适应性变化的重要因素，也是促使鲸类TLR 4中某些识别病原微生物的氨基酸位点在差异显著的环境中发挥新的功能，从而增强鲸类适应和生存的适应性的重要因素。
BackgroundCetaceans (whales, dolphins and porpoises) are a group of adapted marine mammals with an enigmatic history of transition from terrestrial to full aquatic habitat and rapid radiation in waters around the world. Throughout this evolution, the pathogen stress-response proteins must have faced challenges from the dramatic change of environmental pathogens in the completely different ecological niches cetaceans occupied. For this reason, cetaceans could be one of the most ideal candidate taxa for studying evolutionary process and associated driving mechanism of vertebrate innate immune systems such as Toll-like receptors (TLRs), which are located at the direct interface between the host and the microbial environment, act at the first line in recognizing specific conserved components of microorganisms, and translate them rapidly into a defense reaction.ResultsWe used TLR4 as an example to test whether this traditionally regarded pattern recognition receptor molecule was driven by positive selection across cetacean evolutionary history. Overall, the lineage-specific selection test showed that thedN/dS(ω) values along most (30 out of 33) examined cetartiodactylan lineages were less than 1, suggesting a common effect of functional constraint. However, some specific codons made radical changes, fell adjacent to the residues interacting with lipopolysaccharides (LPS), and showed parallel evolution between independent lineages, suggesting that TLR4 was under positive selection. Especially, strong signatures of adaptive evolution on TLR4 were identified in two periods, one corresponding to the early evolutionary transition of the terrestrial ancestors of cetaceans from land to semi-aquatic (represented by the branch leading to whale + hippo) and from semi-aquatic to full aquatic (represented by the ancestral branch leading to cetaceans) habitat, and the other to the rapid diversification and radiation of oceanic dolphins.ConclusionsThis is the first study thus far to characterize the TLR gene in cetaceans. Our data present evidences that cetacean TLR4 has undergone adaptive evolution against the background of purifying selection in response to the secondary aquatic adaptation and rapid diversification in the sea. It is suggested that microbial pathogens in different environments are important factors that promote adaptive changes at cetacean TLR4 and new functions of some amino acid sites specialized for recognizing pathogens in dramatically contrasted environments to enhance the fitness for the adaptation and survival of cetaceans.
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影响因子：
10.7
作者：
Ding, KY;Zhou, K;Shen, Y
通讯作者：
Shen, Y
影响因子：
1.9
作者：
Geisler, Jonathan H.;Sanders, Albert E.
通讯作者：
Sanders, Albert E.
影响因子：
10.7
作者：
Alcaide, Miguel;Edwards, Scott V.
通讯作者：
Edwards, Scott V.
DOI：
10.1073/pnas.96.18.10261
发表时间：
1999-08-31
影响因子：
11.1
作者：
Nikaido, M;Rooney, AP;Okada, N
通讯作者：
Okada, N
与社会性有关的鲸鱼的音调声音产生的系统发育回顾。
影响因子：
3.4
作者：
May-Collado, Laura J.;Agnarsson, Ingi;Wartzok, Douglas
通讯作者：
Wartzok, Douglas