极端与亚极端环境下沙芥属两姊妹种物种分化的遗传基础研究

Speciation has been assumed to be a ‘mystery of mysteries’. The developments of the ‘genic speciation’ concept and interspecific divergences at the genomic level provide a solid basis for solving this mystery. The best model for such an aim is to examine genomic divergences at the population level of the sister species distributed in the different habitats, which is also one of the critical fields in the microevolution. In this project, we aim to re-sequence population samples of two Puginum sister species, distributed respectively in the arid mobile sands and the sub-arid fixed sands based on the finished de novo genomes of two species. Then, we will examine the genomic differentiation between these two species, determine ‘divergence islands’ and annotate the genes in these highly differentiated regions. We will classify the possible functions of the highly diverged alleles and examine their correlations with adaptive and morphological differences of two species. Finally, we will test functional and morphological differentiations of the critical alleles through the transgenic and other approaches. The speciation pattern between two species will be examined and tested by modeling genomic polymorphisms using multiple approaches. This project will not only provide a good case for studying genetic bases of speciation, but also be used as an example to look for gene resources in the arid habitats.

物种形成是进化生物学研究中的谜中之谜。近年来“基因物种形成”概念的形成和基因组水平物种分化方法的成熟为解决这一进化之谜提供了重要基础。姊妹物种在不同生境的群体基因组分化是研究这一科学问题的最好模式，同时也是微进化研究急需发展的重要方向。本项目以分布在流动沙漠极端环境与固定沙丘亚极端环境下的一对沙芥属姊妹种为对象，以完成的两个物种基因组为基础，通过多个体重测序方法，获得两个物种群体基因组水平上的高度分化“岛屿”区域，进而研究这些区域所含基因的性质、相互作用途径及其与两个物种适应不同环境、形态特征差异等之间的相关性；然后选择适应性分化中最为重要的关键等位基因，通过转基因等方法对其序列变异导致的功能差异进行验证。基于群体基因组多态性，用多种方法模拟和验证两个物种的分化过程。本研究不仅能为植物物种形成微进化的分子机制提供重要例证，而且也将为利用非模式生物寻找适应极端环境的基因资源提供新途径。

本项目以分布在流动沙漠极端环境与固定沙丘亚极端环境下的一对沙芥属姊妹种为研究对象，利用群体遗传学方法，在基因组水平上研究了两个姊妹物种高度分化的“岛屿”区域。结合两个物种的形态特征和生境差异，我们在这些区域中发现了一些可能与适应性分化相关的关键等位基因。此外，基于单核苷酸多态性频谱，我们拟合了两个物种分化过程中与基因流相关的各种模型，其中最优拟合模型支持沙芥属姊妹种分化过程中出现了二次接触，说明基因流可能对物种形成有一定的促进作用。本研究为植物物种形成微进化的分子机制提供重要例证，而且也为利用非模式生物寻找适应极端环境的基因资源提供新途径。