基于线粒体基因组的藏马高原适应及系统发育分析

研究测定了西藏那曲（4，500m）、云南中甸（3，300m）、云南德钦（3，300m）地区3匹藏马线粒体全基因组序列。3个地区的藏马线粒体基因组全长以及结构均与韩国济州岛的马类似，但比瑞典马线粒体基因组短。藏马基因组在DNA序列上的两两相似性达993％。通过对线粒体蛋白编码区的分析发现，NADH6基因的蛋白序列在三匹藏马中均表现快速进化的现象。这表明NADH6基因在藏马高原适应进化过程中扮演着重要角色。此外，利用7匹藏马的D—loop区域序列以及与其亲缘关系较近的马的序列首次构建的藏马的系统发育树显示，那曲藏马与中甸、德钦藏马属于不同的分支，且存在较大的遗传多样性，表明藏马可能为多地区起源。

High Altitude Adaptation and Phylogenetic Analysis of Tibetan Horse Based on the Mitochondrial Genome

To investigate genetic mechanisms of high altitude adaptations of animals living in the Tibetan Plateau, three mitochondrial genomes (mt-genome) of Tibetan horses living in Naqu (4,500 m) of Tibetan, Zhongdian (3,300 m) and Deqin (3,100 m) of Yunnan province were sequenced. The structures and lengths of these three mt-genomes are similar to the Cheju horse, which is related to Tibetan horses, but little shorter than the Swedish horse. The pair-wise identity of these three horses on nucleotide level is more than 99.3%. When the gene encoding the mitochondrial protein of Tibetan horses was analyzed, we found that NADH6 has higher non-synonymous mutation rate in all of three Tibetan horses. This implies that NADH6 may play a role in Tibetan horses' high altitude adaptation. NADH6 is one of the subunits of the complex I in the respiratory chain. Furthermore, 7 D-loop sequences of Tibetan horse from different areas were sequenced, and the phylogeny tree was constructed to study the origin and evolutionary history of Tibetan horses. The result showed that the genetic diverse was high among Tibetan horses. All of Tibetan horses from Naqu were clustered into one clade, and Tibetan horses from Zhongdian and Deqin were clustered into others clades. The first molecular evidence of Tibetan horses indicated in this study is that Tibetan horse population might have multiple origins.