海洋哺乳动物苦觉受体基因的进化及其生态学意义

Marine mammals, which include cetaceans (whales,dolphins and porpoises), pinnipeds (seals, sea lions and walrus),sirenians (sea cows) and fissipedians (otters and polar bear), form a diverse group that rely on the ocean,in which many species are endangered. Multiple lines of evidence showed that the ancestors of marine mammals were terrestrial species,who experienced significant changes in morphology and physiology in order to adapt to the marine habitat within such a short time, the molecular and genetic basis underlying the morphological and physiological changes remain unclear. Therefore, marine mammals are good candidates to explore the mechanisms of aquatic adaptation. Taste perception includes sweet, umami, bitter, sour and salty taste modalities, which provide important dietary information. Of the five basic taste modalities,bitter taste is able to avoid toxins and thus is vital for the survival of animals.In this work, we will sequence bitter taste receptor genes (Tas2rs) in 13 marine mammals and undertake evolutionary analysis in combination with publicly available genome data, we aim to characterize the sequence variation and evolutionary patterns of Tas2rs, and date the formation of Tas2r pseudogenes, and describe the distribution of intact Tas2rs. We will discuss how aquatic lifestyle, dietary preferences and other ecological factors drive the evolution of the taste receptor genes. This work will broaden our knowledge of ecology and evolution in marine mammals.

海洋哺乳动物是指依赖于海水环境生存的兽类，包括鲸类、鳍脚类、海牛类和裂脚类等128个物种，其中大多数物种为珍稀保护动物。多项证据均表明，海兽的祖先是陆生哺乳动物，在较短时间内从陆地进入水里生活。为了适应海水生活，海兽在短时间内发生了巨大的生理和形态上的变化，其内在的分子和遗传学基础具有重要的研究价值。味觉分为甜、鲜、苦、酸和咸5种基本感觉形式，赋予了动物判断食物性质的能力。其中，苦觉能阻止动物摄食有害食物，是避免有害食物危害的防御机制之一，因而对海兽在水中的生存至关重要。本研究拟对13个海兽代表物种的苦觉受体基因家族（Tas2rs）进行序列测定和分子进化分析，再结合对已公开基因组数据的分析，揭示海兽苦觉受体基因的序列变异和进化模式，估算Tas2r假基因的形成时间，阐释Tas2r完整基因的分布特点，进而探讨食性、水生生活方式和其它生态因素在海兽苦觉进化中的作用和分子机制。

海洋哺乳动物（即海兽）是指依赖于海水环境生存的兽类，包括鲸类、鳍脚类、海牛类等。多项证据均表明，海兽的祖先是素食的陆生哺乳动物，在较短时间内从陆地进入水里生活，食性同时转变为以鱼类为主。本项目的主要研究内容是：从味觉受体基因进化的角度理解海兽发生快速食性转变的分子机制。本项目以鲸类为主要研究对象，发现基因突变破坏了鲸类基本的味觉系统，五个主要味觉功能中失去了四个，仅仅保留了咸觉，使它们成为第一类失去味觉系统的大部分功能的哺乳动物。论文发表于分子进化领域重要期刊 (Genome Biololgy and Evolution, 2014)，《Science》 以“Whales can’t taste anything but salt”为题进行了在线报道，同时被《Genome Biololgy and Evolution》的编辑作为当期亮点文章以“Highlight: A matter of taste—whales have abandoned their ability to taste food”为题进行了推介。在本项目的研究基础上，我们还探索了吸血蝙蝠、企鹅和48种鸟的味觉基因进化，论文分别发表于英国皇家科学院院刊（Proceedings of the Royal Society B: Biological Sciences, 2014）、生物类综合期刊（Current Biology, 2015）和分子进化专业期刊（Genome Biology and Evolution, 2015）。