蚓果芥的分子谱系地理学和对干旱环境的适应性进化研究

During the Quaternary periods, geology and climate changed severely, the desert areas increased extremely in the northern China, and the distribution ranges of majority of species have been changed in this area, thereby the species population genetic structure was affected. Standing genetic structure of extant species could reflect its population dynamics history in the past, which representing the historical geographic events of its habitat. Little is known about how plant species native to deserts react the impact of climate change so far. Braya humilis, a widespread Cruciferous plant in the northern arid regions of China, was chosen as a model to address the question like this. Combined with Sanger sequencing and next-generation sequencing (NGS), three kinds of molecular markers (chloroplast DNA, SSR, and nuclear genes) with different genetic backgrounds and evolutionary rates will be used to investigate the level and pattern of genetic variation within and among natural populations and to reconstruct the past demographic history with coalescent simulation. In addition, NGS will be utilized in this project to analyze the nucleotide diversity of population amplicon pools, which represent all the potential candidate genes involved in flowering regulatory network and drought stress signaling pathway, and neutrality tests based on statistic mode of coalescent theory will be conducted to reveal the molecular mechanisms of B. humilis to adapt to the continued deteriorated arid environment and the dramatic climate change. Combining the methodologies of phylogeography and adaptive evolution, this project will shed a light on the knowledge of a plant how to react the climate and geological change in the past and may direct the understanding of drought adaptation mechanism in the North China.

第四纪以来，我国北方地区地质气候变化剧烈，荒漠大面积增加，多数物种分布区发生改变，进而影响了物种的种群遗传结构。根据现存物种的遗传结构，可以回溯其群体动态历史，推演其分布区经历的历史事件。本项目拟以北方干旱区广布草本十字花科蚓果芥为研究材料，结合传统测序和二代测序技术，运用三种不同遗传背景和基因流速度的分子标记（叶绿体、SSR和核基因）研究其遗传变异分布式样，根据溯祖理论构建其群体进化历史，揭示其对北方过去气候波动与环境变迁的响应模式。此外，本项目拟运用群体建库二代测序的方法，进一步分析开花调控网络和干旱胁迫信号通路相关基因的核苷酸变异式样，基于溯祖理论的种群统计进化模型，探寻蚓果芥对持续恶化的干旱环境与剧烈气候变化适应性进化的分子机制。本项目将分子谱系地理学和适应性进化有机结合，将为进一步澄清北方干旱区成因和理解植物干旱生态环境适应性机制奠定理论基础。

本项目旨在揭示蚓果芥的动态进化历史以及探寻其对干旱环境适应性进化的潜在机制。基于不同分子标记序列变异，我们认为青藏高原应为蚓果芥的多样性中心。蚓果芥具有明显的谱系结构，群体之间基因流被有效阻断，而生境片段化可能是导致蚓果芥适应性辐射的主要因素。通过分析蚓果芥自然群体间组成型基因表达差异和序列分化，我们认为非生物胁迫是蚓果芥局域适应性的主要驱动力，而不同的开花策略是蚓果芥适应北半球不同气候带和纬度环境的主要手段。同时，线粒体基因组对于蚓果芥的物种形成以及适应青藏高原及其周边干旱区域的作用不容忽视。此外，蚓果芥具有较高的干旱耐受能力，抗氧化相关酶活呈现不同的生理响应模式，其对应基因表达模式与酶活动态变化有一定的相关性。以上研究结果为我们进一步深入理解植物干旱生态环境适应性机制奠定了理论基础。