基于线粒体基因组的鼠兔高海拔适应机制探讨

Discussion on the Mechanism of High-altitude Adaptation in Pika Based on Mitochondrial Genome

鼠兔隶属于兔型目,大多生活在海拔较高的地区,是研究哺乳动物对高寒缺氧环境适应机制的理想模型。线粒体通过氧化磷酸化产生能量,在机体的氧气利用和能量代谢中发挥重要作用。本研究测定了柯氏鼠兔线粒体全基因,然后分析了5种分布于较高海拔的鼠兔与6种较低海拔的兔科物种的线粒体基因组,并探讨了鼠兔高海拔适应时线粒体基因的作用。研究表明相比于较低海拔物种,鼠兔积累了更多的非同义突变,并且在鼠兔的线粒体编码基因的NADH2、NADH4L、NADH4、NADH5、NADH6、Cytb上均检测到正选择信号。ND2、ND4和ND5亚基的正选择位点位于非跨膜区,鼠兔的ND4L、ND6亚基的正选择位点位于TM区,但并不在与质子转运相关的关键区域。NADH脱氢酶亚基可能通过氨基酸变异干扰了质子转运过程的有效性。Cytb上的正选择信号位于跨膜螺旋H,氨基酸的变异可能影响到泛醇的结合与转移,进而改变了能量代谢。

Pikas belong to the Order of Lagomorpha, which live in the region of high altitude, are considered the ideal animal model for cold and hypoxia adaptation studies. Mitochondria, which produces energy by oxidative phosphorylation, plays an important role in oxygen utilization and energy metabolism of the body. In this study, we determined the complete gene of the O. koslowi mitochondrial, analyzed the mitochondrial genome between 5 kinds of pikas distributed in the higher altitudes and 6 species of Leporidae in lower-elevation areas, and then discussed the roles of mitochondrial genome of pikas in the adaption to high altitude. The research indicated that the pikas accumulated more nonsynonymous mutation. The positive selection signals were detected in the NADH2, NADH4 L, NADH4, NADH5, NADH6 and Cytb genes of mitochondrial genome in the pikas. The positive selection sites of ND2, ND4 and ND5 were located in the non-transmembrane regions. The positive selection sites of ND4 L and ND6 were seated in the TM regions, these sites were not at the critical section related to the proton transport. The mutation of amino acid in NADH dehydrogenase subu nits may interference the validity of the process of proton transport. The positive selection signal of Cytb is located in the transmembrane helix H. The mutation of amino acid could affect the combination and transfer of panthenol, and then changes the energy metabolism.