| The Bald’s Toad-headed Agama (Phrynocephalus theobaldi) lives in Tibetan Plateau, and makes a suitable model animal to study the hypoxia adaptation of ectotherms in high altitude. In this thesis, I aim to explore the molecular mechanism of hypoxia adaptation in lizards by comparing the pathways of energy metabolic using transcriptome sequencing between the Bald’s Toad-headed Agama and a close-related species, the steppe toad-headed Agama, Phrynocephalus frontalis. I then studied the expression patterns of HIF1α and HIF2agenes and their downstream and upstream genes in these two species using real-time fluorescence quantitative techniques to explore the role of HIF pathway in hypoxia adaptation.The transcriptome analysis of lizard liver demonstrated that there were 71,079 transcript and 54,454 Unigenes in P. theobaldi, and 73,148 transcript and 57,752 Unigenes in P.frontalis. I found 7,964 orthologous genes and 237 positively-selected genes, of which five common positively-selected genes including PPA、ATPeF1O、 ATP5EP2、ATP6V1E1、NDUFAB1 located at different complexes of oxidative phosphorylation. This result indicates that P. theobaldi experiences strong positive selection on energy metabolism that may play an important role in hypoxia adaptation.The mRNA expression of HIF2a and TF in liver decreased as altitude increases, and HIF2a expression was higher in P. theobaldi than in P. frontalis. The mRNA expressions of HIFla and HIF2a were higher in the high-altitude population than the high-altitude population in P. theobaldi, with no difference between P. theobaldi than in P.frontalis. The expression of EGLN1 expression did not differ between or within species.Therefore, our studies indicate that P. theobaldi adapt to hypoxia in high altitude by adjusting the energy metabolism. In addition, the expression of HIF pathway differ between different tissues of liver and heart in P. theobaldi. |
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