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题名	线粒体基因组的变异与哺乳动物高原适应性
作者	徐树青
学位类别	硕士
答辩日期	2007-01
授予单位	中国科学院研究生院
授予地点	北京
导师	王文 ; 郑晓光
关键词	线粒体基因组 藏羚羊 高原鼠兔 藏马 进化历史 青藏高原 高原适应
其他题名	Mitochondrial genome variation and adaptation to high altitude of mammals
学位专业	细胞生物学
中文摘要	青藏高原是世界上最大、最年轻的高原。大气氧分压低、太阳辐射强烈和气候寒冷等自然特点使得生活在青藏高原上的动物在形态、生态、行为以及生理机能上都受到深刻的影响，并在进化过程中对高原环境产生了特殊的适应性。生活在高原上的动物分为世居动物和移居动物，它们处于高原适应过程中的不同阶段，并且有着不同的高原适应性的特点。为了研究高原哺乳动物所拥有的特殊高原适应性的遗传基础和进化历史，以及探讨处于不同高原适应阶段的哺乳动物对高原的适应性在遗传基础上的异同，本研究首次测定和分析了高原世居动物中的藏羚羊（Pantholops hodgsonii）和高原鼠兔（Ochotona curzoniae）以及高原移居动物中的藏马（Equns caballus）这三种具有代表性的高原动物的线粒体全基因组。 1. 藏羚羊线粒体DNA中的变异及其进化史 在对线粒体上13个基因进行了进化分析后，我们发现细胞色素氧化酶1（COX1）基因在藏羚羊和牦牛中都有高的非同义突变的现象。COX1基因编码的蛋白是线粒体氧化呼吸链上复合物Ⅳ的一部分，它将电子传递给氧，进行有氧呼吸并产生能量。考虑到藏羚羊与牦牛都是生活在相同的气候环境中，我们猜想线粒体基因组编码的COX1基因的进化可能对青藏高原世居动物适应高原环境起到作用。藏羚羊的线粒体DNA数据表明，藏羚羊与绵羊、山羊的亲缘关系较近，而与羚羊属家族的动物则相对较远，同时我们估算了藏羚羊与绵羊山羊的分化时间大约为220万年左右。这一时间与一些学者所估计的青藏高原隆起时间大致吻合。 2. 高原鼠兔线粒体DNA中的变异及其进化史 对高原鼠兔线粒体基因组上的基因进行进化分析后发现，对于高原鼠兔这一分枝上，COX1基因也有高的非同义突变速率。这表明COX1基因在高原鼠兔适应青藏高原高寒缺氧的环境过程中也可能受到选择压力的作用，结合我们在藏羚羊和牦牛中的分析结果，我们推测高原世居动物在COX1基因的进化过程中很多都表现出类似的受选择现象。 3. 藏马线粒体DNA中的变异及其进化史 我们测定了西藏那曲(4500m)、云南中甸(3300m)、云南德钦(3300m)地区共三匹藏马线粒体全基因组序列。通过对线粒体蛋白编码区的分析发现，与藏羚羊、高原鼠兔等高原世居动物表现出的COX1基因受选择不同，在三匹藏马中NADH6基因均表现高的非同义突变现象。NDAH6基因编码的蛋白是线粒体氧化呼吸链上复合物Ⅰ的一部分，它催化电子从NADH传递给辅酶Q。不同地区藏马中NADH6基因类似的进化方式表明NADH6基因的进化可能与藏马对高原极端环境的适应有关。藏马在线粒体基因进化上所表现出的与其它高原世居动物的不同究竟是由于动物在适应高原的不同阶段其遗传基础和策略的不同所造成的，还是由于物种间的差异所造成的我们尚不能确定。还需要进一步对高原动物线粒体基因进行研究。此外，我们对藏马进化史的研究表明藏马可能为多地区起源。
英文摘要	The Qinghai-Tibetan Plateau is the largest and youngest high land in the world. Because of its particular environment of the high altitude, like hypoxia, coldness and high radiation, animals living on the high land were forced to undergo adaptive changes in morphology, behavior, ecology, physiology and genetics. These animals have acquired particular adaptation traits to the environment of high altitude. To study the genetic basis of those traits and evolutionary history of high altitude animals, we sequenced and analyzed mitochondrial genomes (mt-genome) of three representative high altitude animals: Tibetan antelopes (Pantholops hodgsonii), Tibetan horses (Equns caballus), and plateau pikas (Ochotona curzoniae). The results are as followings: 1. mt-genome and high altitude adaptation of the Tibetan antelope (Pantholops hodgsonii) Analysis on mitochondrial DNA mutations indicates that the COXI (cytochrome c oxidase subunit I) gene has higher non-synonymous mutation rate in Pantholops hodgsonii and Bos grunniens. COX1 is one of the subunits of complex Ⅳin respiratory chain, which transfers electrons to oxygen and generates ATPs. Considering the same climate and environment shared by these two mammalian species, we proposed that the mitochondrial COXI gene is probably relevant for these native mammals to adapt to the high altitude environment. Based on the mitochondrial DNA sequence data, the estimated divergence time between Pantholops hodgsonii and Ovis aries is about 2.25 million years ago, which is closed to the estimated time of the Qinghai-Tibet plateau uplift. 2. The mt-genome of the plateau pika (Ochotona curzoniae) The full length mitochondrial genome of plateau pika (Ochotona curzoniae) is 17566bps, which is longer than American pikas (Ochotona collaris and Ochotona princes) (16968bp & 16481bp respectively). The variation of the mitochondrial genome length is caused by the different copy number and types of repeat fragments. After analyzing the protein coding genes in the mitochondrial genome, again we found that COX1 gene has a higher non-synonymous mutation rate on the branch of Ochotona curzoniae. This indicates that COX1 may be also under selection during the adaptation process of Ochotona curzoniae to the environment of high altitude. 3. mt-genome and estimatary history of Tibetan horses (Equns caballus) We sequenced three mt-genomes of Tibetan horses collected from Naqu (4500m) of Tibetan, Zhongdian (3300m) and Deqin (3100m) of Yunnan province. The structure and length of these three mt-genomes are similar to the Cheju horses. Different from COX1 under selection in the Tibetan antelope and plateau pika, when analyzing the mitochondrial protein coding genes of Tibetan horses, we found NADH6 has higher non-synonymous mutation rate in all of three Tibetan horses. This implies that NADH6 may play a role for Tibetan horses’ high altitude adaptation. NADH6 is one of the subunits of complexⅠin respiratory chain. Although both of NADH6 and COX1 located in respiratory chain, they belong to different complexes and play different roles for respiratory chain. Whether the different evolution patterns of mitochondrial genes caused by different adaptive genetic basises of animals or by other reasons is unclearly. Further works should be undertaken to answer this question. Furthermore, the study of evolutionary history of Tibetan horses suggests that the extant Tibetan horse populations may have multiple origins.
语种	中文
公开日期	2010-10-14
内容类型	学位论文
源URL	[http://159.226.149.42:8088/handle/152453/6103]
专题	昆明动物研究所_基因起源组
推荐引用方式 GB/T 7714	徐树青. 线粒体基因组的变异与哺乳动物高原适应性[D]. 北京. 中国科学院研究生院. 2007.

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