沙蜥高海拔适应的遗传基础：基因序列和表达谱的比较研究

High-altitude environments provide an ideal system to study "adaptation", a core issue in modern evolutionary biology. The genetic basis of high-altitude adaptation serves as the foundation for understanding the adaptive mechanism of living a plateau life. Currently, most of the studies on high-altitude adaptation are focused on endotherms, but poikilotherms,which account for the important part of biodiversity, have not acquired enough attention. Reptiles are one of the main groups of terrestrial vertebrates, which belong to poikilotherms but share a series of common traits with endotherms. Therefore, reptiles represent excellent models for studying high-altitude adaptation because they can be easily compared to well-studies endotherms. In this project, we propose to examine eight species of toad-headed lizards (Phrynocephalus) and to study the genetic basis of high-altitude adaptation of reptiles. First, we will detect candidate genes that have been subjected to natural selection along the high-altitude branches of toad-headed lizards by transcriptome sequencing and molecular evolution analysis. Second, we will identify differentially expressed genes and establish the relationship between gene expression and phenotypic plasticity for toad-headed lizards at various altitudes by a reciprocal transplant experiment and expression profile sequencing. Toad-headed lizards are capable of surviving at the highest altitudes among lizards and are true high-altitude dwellers.We hope to find genetic evidence of adaptation to high altitudes at both gene sequence and expression levels, which will lay a solid foundation for further studies on mechanisms of adaptation in reptiles.

生物对高海拔环境的适应，为研究“适应”这一现代生物学的核心问题提供了一个极佳的研究体系；它的遗传基础，则是全面了解生物高海拔适应机制的前提。目前的高海拔适应研究大多集中于内温动物，而对占据生物多样性重要地位的外温动物的研究仍处于起步阶段。爬行动物是陆生脊椎动物的一个重要类群，它们属于外温动物，但又与内温动物共享许多特质，利于二者之间的比较，因此是研究生物高海拔适应的理想物种。本项目选择沙蜥属的8种蜥蜴为研究对象，首先通过转录组测序和分子进化分析，检测其在高海拔支系上受到自然选择作用的基因；然后通过从低海拔到高海拔的移植实验和基因表达谱测序，找出不同海拔环境下它们的基因表达差异，并建立差异表达基因与表型可塑性之间的关系。沙蜥是世界上海拔分布最高的蜥蜴，我们希望找到它们从基因序列到基因表达的不同水平上一系列与高海拔适应有关的遗传证据，为进一步探索爬行动物的高海拔适应机制打下坚实的基础。