海洋哺乳动物尿素转运蛋白关键基因——SLC14A2的分子进化

Molecular Evolution of SLC14A2,a Key Gene for Urea Transporters in Marine Mammals

趋同进化是进化生物学中的核心科学问题.独立起源的海洋哺乳动物不同类群为了适应高渗的海洋环境,产生了趋同的渗透调节适应机制,能够产生高度浓缩的尿液.本研究选取了编码尿素转运蛋白的SLC14A2基因为候选基因,进化分析发现该基因在海洋哺乳动物中发生了显著的加速进化,鉴定到4个正选择位点(35、463、592、598)至少被两种最大似然法(maximum likelihood,ML)方法检测到,且这些位点位于或临近重要的结构域,表明海洋哺乳动物可能通过增强肾脏对尿素的主动运输功能从而产生高度浓缩的尿液,与先前的生理研究结果一致.特别重要的是,在海洋哺乳动物不同类群间鉴定了6个平行/趋同进化位点,进一步为海洋哺乳动物产生高度浓缩的尿液以适应海洋环境提供趋同的分子证据.另外,正选择主要集中在鲸类进化谱系,可能与鲸类完全营水生生活面临更大的渗透调节的压力有关.本研究通过对SLC14A2基因的进化分析初步揭示了海洋哺乳动物为了适应高渗的海洋环境产生高度浓缩的尿液提供了趋同的分子机制.

Convergence evolution is the core scientific issue in evolutionary biology.In order to adapt to the hyperosmotic marine environment,independent-originated-marine mammals have evolved the convergent osmoregulation mechanism through producing highly concentrated urine.In this study,the SLC14 A2 gene encoding urea transporter was used as a candidate gene for evolutionary analysis.The results revealed that this gene has undergone significant accelerated evolution in marine mammals.Four positively selected sites(35,463,592,598)were detected by at least two maximum likelihood(ML)methods,and these sites were located or near important functional domains.It indicates that marine mammals may produce highly concentrated urine from enhancing the active transport of urea by kidneys,which is consistent with what has been found in the previous physiological studies.Especially,the study identified 6 parallel/convergent evolutionary sites among different groups of marine mammals,which has provided convergent evidence of marine mammals producing highly concentrated urine to adapt to the marine environment at the molecular level.In addition,the positive selection is mainly focused on the evolutionary lineage of cetaceans,which may be related to cetaceans faced greater osmotic pressure than other marine mammals because cetaceans have adapted to fully aquatic life.In this study,the evolutionary analysis of the SLC14 A2 gene in marine mammals provides a convergent molecular mechanism of marine mammals to produce highly concentrated urine for adapting to the hypertonic marine environment.