Studies On The Evolutionary Molecular Mechansim Of Adadtation Of Animals Native To The Plateau For Galliformes,Rodentia And Lagomorpha

The biological diversity of nature is result of evolution of biology’s special characters for adaptation to the environments. Natural selection plays a key role in adaptive evolution of biology, which makes it become the most important part in biology since Darwin period. It is urgent to uncover genetic mechanism underlying the complex adaptive phenotype from relation between natural selection and adaptive evolution on the molecular level with increasingly sophisticated phylogenetic relationships and adaptive phenomenons. Here, taken high-altitude indigenous Galliformes, Rodentia and Lagomorpha animals as examples, combination the informations of the sequences, expression pattern and next generation sequencing, we successfully validate adaptive evolution mechanism of animals native to the plateau from the visions of candidate genes, important positions within pathway, and metabolic pathway separately.Because birds are high energy consumption animal while hypoxia restrict energy supply on plateau, lots of changes in birds native to high-altitudes must occurr to adapt to hypoxia. As energy metabolism factory, mitochondria make various contributions on animals’ adaptation to high-altitudes. We guess it is possible that mitochondrial genomes of high-altitude indigenous birds play an important role during adaptation to high-altitudes. We obtained22the mitochondrial genomes of birds and systematically survey phylogenetic relationships and selective pressures of13mitochondrial genes coding sequences for high-altitude galliformes species. We found at least four lin-eages that independently occupied this high-altitude habitat. Selective analyses revealed significant evidence for positive selection in the genes ND2, ND4, and ATP6in three of the high-altitude lineages. This result strongly suggests that adaptive evolution of mitochondrial genes played a critical role during the independent acclimatization to high altitude by galliform birds. The changes at positive selected sites may impact structures and functions of protein, so additional research with functional assays is needed to identify how these changes affect metabolism.Adaptive evolution of mammals native to high plateaus is a hot spot in biology research. The previous studies showed that genes being associated with ATP utilization, DNA repair, and blood and vessel processes play vtial role in adaptation to the plateau. However, researches that have focused mainly on either a single plateau mammalian species or on a few genes have some limitations, which can’t involve combined actions from many genes or common pathway of different species underlying complex phenotype adaptation. In the4th chapter, we screened26genes that are associated with ATP utilization, DNA repair, and blood and vessel processes in7species of native plateau mammals. Signals of parallel evolution were detected in three genes (Alkbh3, Mylk2, and Men1) in four plateau lineages (pikas, plateau zokor, Chinese scrubby vole, and Sichuan field mouse). The three genes with signals of parallel evolution might play roles in providing resistance to the high levels of UV and hypoxia that are experienced by the divergent lineages of mammals native to the Tibetan plateau. In addition, significant signals for positive selection were detected in five genes (Eief2b4, Agt, Ca4, Nbn and Polk) in pikas. Among the putatively adaptively evolving genes, four (Alkbh3, Menl, Polk, and Nbn) are involved in DNA repair, three (Ca4, Agt, and Mylk2) in blood and vessel processes, and one (Eif2b4) is related to the production of energy. These results provide evidence that adaptation to the plateau is complex and that multiple pathways and mechanisms (parallel evolution and positive selection) are involved.Considering limitations of candidate gene while high-efficient of transcriptome analysis, we obtained six transcriptome of small mammals native to the plateau to analyze sequence variants and expression pattern for coding genes within the whole genome in5th chapter. Our results showed that genes in many life processes of small mammals native to high altitude have undergone adaptive sequence changes or up-regulated expression to vercome the extreme conditions of high-altitude (e.g., hypoxia, cold, and high UV). It is involved in fat and alcohol metabolism, radiation resistance, hypoixa and immunological adaptation, cell apoptosis and regeneration, reproduction and so on. Interestingly, hypoxia-inducible factor2a (EPAS1) was firstly found undergoing multiple parallel evolution and up-regulated expression in mammals native to the plateau. In addation, we have conducted a low-altitude domesticating experiment for Ochotona curzoniae and found that genes referring to fat and alcohol metabolism and UV resistance had undergone down-regulated expression while genes in immunological adaptation and ionizing radiation resistance had showed up-regulated expression. For domestic O.curzoniae, changes of expression pattern provide supports for fastly adaptation to low-altitude environment. The identification of key genes involved in the adaptation to the plateau environment may provide some perspective for prevention and treatment on plateau diseases. Future studies on combination between these adaptation machenisms and human diseases may contribute to a detailed understanding of these important physiological mechanisms with relevance to human medical conditions (for example, the links between alcoholism and alcohol metabolism, hypoxidosis and hypoxic response, fat metabolism and obesity, and canceration and radiation resistance respose) and improve these studies. In above studies, multiply adaptive evolutions in few research non-model animals are investigated from various aspects:from the pure analysis of phylogeny and selective pressure on the candidate gene coding sequence, to mitochondrial genome research, then developed with sequence variants and expression pattern for coding genes within the whole genome. Our study visions varied from the common adaptive characters (parallel or convergent evolution) to specific adaptive mechanisms (positive selection or differential expression), which effectively reveal adaptive characters and molecular evolution of genetic mechanism in animals native to the plateau.