沙蓬干旱响应相关基因调控网络的适应性分化研究

As a primary and pioneer plant species in the reversal process of desertification, Agriophyllum squarrosum plays a key role in the succession of desert ecosystems. Moreover, A. squarrosum has high edible value and medicinal functions. Previous biogeographic analysis and common garden experiment on A. squarrosum showed that significant differentiation had occurred on both of the genetic variations and phenotypic traits among its natural populations with different rainfall patterns. Furthermore, RAD-seq genotyping of the natural populations of A. squarrosum indicated some SNPs were involved into adaptive differentiation along the rainfall gradient. Unfortunately, the molecular mechanisms of how A. squarrosum responds to drought stress and the genetic basis of its adaptive divergence among the populations with different rainfall are still unclear. In this proposal, based on the integrating transcriptomics and metabolomics, we aim to investigate the molecular metabolic regulation network of drought-tolerance response of A. squarrosum. Then, we try to analyze the genetic diversity on candidate genes and reference genes among the natural populations of A. squarrosum and to screen the adaptive allelic variations. Combined with the association analysis of the ecological factors and genetic variations for each population, we try to address the molecular ecology mechanism of A. squarrosum adapted to the desert environment heterogeneity along the precipitation gradients. This study will not only supply qualitative assessments and practical theory for maintaining and improving the stability of desert pioneer plant populations, but will also provide elite germplasm resources for the breeding and selection of potential food crops mitigating the global climate change. It will also provide basic data for promoting the development of ecological restoration and agricultural models in desert areas.

沙蓬是沙漠化逆转过程中的首要建群植物，在荒漠生态系统演替中起关键作用，并且具有药食兼用的功效。前期，我们通过谱系地理研究和同质园实验发现，沙蓬不同群组间在遗传和表型上均发生显著分化，RAD群体测序的结果进一步表明受分布区降水格局不均匀的影响，沙蓬群体间已然发生了适应性分化，但是其干旱响应机制及其适应性分化的遗传机理尚不清楚。因此，本项目拟通过转录组和代谢组等多组学的方法，挖掘抗旱遗传资源并勾画沙蓬抗旱响应的分子代谢调控网络。同时，筛选抗旱候选基因和中性背景基因对沙蓬自然群体进行遗传多样性调查、扫描适应性分化位点，并结合降水生态因子数据进行关联分析，解析沙蓬适应沙丘不同降水梯度变异的分子生态学基础。本研究将不仅为荒漠建群植物种群稳定性的维持与改善提供定性评价和因地制宜的实践方案，还能为选育应对全球气候变化的潜在粮食作物提供优良种质资源，并为推进沙化土地生态恢复与特色农业模式发展提供基础数据。

沙蓬是广布我国各大沙漠/地的首要建群植物，具有卓越的抗旱能力以及对降水时空格局变化的适应能力。为了解析其干旱响应机制及其适应性遗传机制，本研究基于RAD-seq群体数据分析了沙蓬的群体遗传结构；通过转录组数据解析了不同降雨梯度下沙蓬生态型间的干旱响应及干旱记忆调控的异同；结合代谢组数据探讨了沙蓬适应水热异质性环境的分子代谢基础。主要结果如下：.1.基于RAD-seq群体遗传数据分析发现，沙蓬可能起源于古尔班通古特沙漠西北部的布尔津县，然后进一步分化为东部支系和中部支系；各支系间生态位彼此独立，遗传与环境因子的关联分析揭示，降水是驱动沙蓬群体遗传分化的重要胁迫因子；.2.通过对沙蓬半干旱区AEX生态型和干旱区WW生态型进行干旱胁迫实验发现，WW生态型对干旱胁迫有更强的耐受性和恢复能力；转录组数据表明两个生态型间有12个共有的参与干旱响应的调控途径；两生态型间有629个基因受到正选择，其中大约73%的正选择基因的表达均与干旱胁迫响应相关，说明不同降雨梯度下的沙蓬生态型间已然发生了适应性分化；.3.WW生态型和AEX生态型多轮干旱胁迫实验表明，沙蓬招募了大量的与过氧化损伤和水分胁迫相关的基因参与其干旱记忆的调控，但两生态型间干旱记忆的强度和调控方式存在显著差异；反复干旱可能会激活沙蓬中的转录因子分子开关，该信号通过次级开关传递和放大，从而调节下游多种代谢途径，使得沙蓬对不可预测的反复干旱胁迫具有更快更强的反应；.4.代谢组数据显示，不同生态型沙蓬间由于长期所受到的干旱、高温等环境因子胁迫程度不同，非特异性的胁迫应激反应调节通路中的部分基因的表达存在显著差异，间接影响黄酮类、有机酸以及萜类等次级代谢产物的累积，从而适应水热异质性沙漠环境。.本项目解析了沙蓬不同生态型间干旱响应机制及分化的遗传机理，初步勾画了沙蓬干旱记忆的分子调控机制，探讨了沙蓬适应干旱等异质性沙漠环境的分子代谢基础，为选育应对全球气候变化的未来作物提供了优良种质和基因资源。