鲸类脂肪代谢相关基因的进化及其与水生适应的关系

发布时间：2018-05-08 00:08

本文选题：鲸类 + 三酰甘油　；参考：《南京师范大学》2016年博士论文

【摘要】：鲸类(Cetacea)是一类在进化上具有十分重要和特殊意义的次生性水生动物,约56-53百万年前其祖先从陆地重返海洋,伴随着形态的巨大改变和快速地适应辐射,形成了丰富多样的现生鲸类。从陆地重返海洋,鲸类面临的首要挑战就是生活介质的改变,由原先的空气变为了水,而水这种高效的热传导体,在相同的温度下,从体内带走热量的速度比空气快25倍。因此对于鲸类而言,一方面面临着严重的热量丧失,必须获取足够的保温物质；另一方面面临环境变迁、季节更替所造成的食物短缺,必须形成独特的代谢机制以获取足够的能量。为了应对这些挑战,鲸类的鲸脂层较其他陆生哺乳动物显著增厚。这个改变在鲸类适应水生生境的过程中具有非常重要的意义,增厚的鲸脂层不仅能够起到保温、保证身体流线型、增加浮力和促进运动等作用,而且更为重要的是能通过脂肪代谢提供机体所需的能量和淡水。显然,鲸类在适应水生生境的过程中,已经形成了完善的鲸脂层增厚及相关的脂肪代谢机制。然而,这一适应的分子进化机制尚不清楚。本研究首次对鲸类脂肪消化、鲸脂层增厚和脂质代谢通路三个方面的基因进行了分子进化分析,试图阐明鲸类脂肪代谢适应性进化历史,并从分子水平上揭示脂肪代谢相关基因与鲸类水生适应之间的关系。论文第二章,研究了在脂肪的消化、溶解和吸收过程中起关键作用的四个消化酶基因(PNLIP、LIPC、LIPF和CYP7A1)在鲸类和其他陆生哺乳动物中的分子进化。结果表明,脂肪消化酶的三个关键基因(CYP7A1、LIPF和PNLIP)在鲸类中受到了强烈的正选择作用,提示这些基因发生了适应性进化,有助于提高对于食物中脂肪物质消化和吸收的能力,从而促进了鲸类食性的转变。同时,CYP7A1和PNLIP两个消化酶基因还在鲸类和食肉目两个枝之间检测到了3个平行／趋同位点,进一步说明了鲸类中的脂肪消化酶基因发生了适应性进化,而且表明鲸类和食肉目动物在脂肪消化方面存在相似性。论文第三章,首次在鲸类代表物种和其他哺乳动物中研究了88个三酰甘油代谢相关基因的分子进化,揭示了三酰甘油代谢相关基因的适应性进化在鲸脂层增厚过程中的关键作用。研究结果发现88个候选基因中的41个被检测到受正选择作用,这些基因分别参与三酰甘油的合成、分解和调控等过程。三酰甘油代谢相关基因存在如此广泛的正选择信号,可能与鲸类鲸脂层的温度调节、浮力控制、保持身体流线型、代谢能量储存和促进运动等重要功能有关。有趣的是,一些阻止脂解的调控基因在鲸类中也检测到了显著的正选择证据,表明鲸类已经进化出了一种有效机制防止鲸脂层被无限制降解,这对鲸类在禁食期维持鲸脂层厚度尤为重要。这些结果表明,鲸类存在有效且复杂的机制来保证鲸脂层维持合适厚度,从而更好的适应水生生活；同时也表明“肥胖”对于人类而言与多种慢性疾病有关,但是对于鲸类则是一种健康状态。论文第四章,对KEGG数据库中整个脂质代谢通路的327个基因进行了研究,全面揭示了脂质代谢通路基因在鲸类水生适应进化过程中的重要作用。结果发现,在鲸类中受正选择作用的149个基因分别位于脂质代谢通路中的15个分通路,并且鲸类的各个枝系都检测到了正选择基因,提示鲸类脂质代谢通路基因发生了持续的适应性进化。结合各个代谢途径的功能,表明脂质代谢通路中TAG合成、脂肪酸分解及多不饱和脂肪酸的代谢等功能都得到了增强,为鲸类更好的适应水生生境并辐射到全球各个水域起到了积极的推动作用。
[Abstract]:Cetacean (Cetacea) is a very important and special class of secondary aquatic animals. About 56-53 million years ago, its ancestors returned from land to sea, accompanied by great changes in morphology and rapid adaptation to radiation, forming rich and diverse cetaceans. The primary challenge facing whales was to live from land to sea. The change in the medium is changed from the original air to the water, and the high efficient heat transfer conductor, which takes away the heat from the body at the same temperature, is 25 times faster than the air. Therefore, for cetaceans, on the one hand, it faces severe heat loss and has to obtain sufficient thermal insulation; on the other hand, it faces environmental changes and seasonal changes. In order to respond to these challenges, cetacean blubber layers are significantly thicker than other terrestrial mammals. This change is of great significance in the process of cetacean adaptation to aquatic habitats. The thickened blubber layer not only protects the body, but also ensures the body. Streamlining, increasing buoyancy and promoting movement, and more important is the energy and fresh water that can be provided through fat metabolism. Obviously, cetacean has formed a perfect blubber layer thickening and related lipid metabolism mechanism in the process of adapting to aquatic habitats. However, the molecular evolutionary mechanism of this adaptation is not yet clear. In this study, the three genes of cetacean fat digestion, blubber layer thickening and lipid metabolism pathway were analyzed for the first time in order to elucidate the evolutionary history of cetacean fat metabolism, and to reveal the relationship between fat metabolism related genes and cetacean aquatic adaptation from the molecular level. In the second chapter, the fat was studied. Molecular evolution of four digestive enzyme genes (PNLIP, LIPC, LIPF and CYP7A1) in cetaceans and other terrestrial mammals during digestion, dissolution and absorption. The results showed that three key genes (CYP7A1, LIPF, and PNLIP) of fat Digestis (CYP7A1, LIPF and PNLIP) were strongly selective in cetaceans, suggesting that these genes were appropriate. Sexual evolution helps to improve the ability to digest and absorb fatty substances in food, thus promoting the transformation of cetaceans. At the same time, the two digestive enzyme genes of CYP7A1 and PNLIP also detected 3 parallel / convergent loci between cetaceans and two branches of carnivores, which further indicated that the fat digestible enzyme gene in cetaceans was suitable. In the third chapter, the molecular evolution of 88 three glycerol metabolism related genes was first studied in cetacean representative species and other mammals, and the adaptive evolution of three acyl glycerol metabolism related groups was revealed in the blubber layer thickening process. The results showed that 41 of the 88 candidate genes were detected by positive selection. These genes were involved in the synthesis, decomposition and regulation of three glycerol respectively. The three glycerol metabolism related genes had such a wide selection signal, which might be associated with the temperature regulation, buoyancy control and body flow of whale whale fat layer. It is interesting that some regulatory genes that prevent lipolysis have also been identified in cetaceans with significant positive evidence that cetacean has evolved an effective mechanism to prevent the blubber layer from being degraded without restriction, which is particularly important for Cetacean blubber thickness during the fasting period. These results suggest that cetacean has an effective and complex mechanism to ensure that the blubber layer maintains appropriate thickness to better adapt to aquatic life; it also indicates that "obesity" is associated with a variety of chronic diseases for humans, but is a healthy state for cetaceans. In the fourth chapter, the whole lipid metabolism in the KEGG database 327 genes in the pathway have been studied to reveal the important role of the lipid metabolism pathway in the adaptation and evolution of cetacean aquatic. It is found that the 149 genes of positive selection in cetacean are 15 pathways in the lipid metabolism pathway, and all the branches of cetaceans have detected the positive selection genes. The genes of cetacean lipid metabolism pathway have sustained adaptive evolution. Combining the functions of various metabolic pathways, it shows that the functions of TAG synthesis, fatty acid decomposition and polyunsaturated fatty acid metabolism in the lipid metabolic pathway have been enhanced, which are active for cetaceans to adapt to aquatic habitats and to radiate all waters around the world. Push the effect.

【学位授予单位】：南京师范大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：Q953

【相似文献】