胡杨耐盐的表观基因组学研究

Soil salinization is one of the most serious environmental factors that affect plant development and growth, limit crop productivity and quality, and even endanger the ecological security. In depth study of tree adaptation to salinity and increasing their stress tolerance have important significance on easing China’s timber supply and demand contradiction as well as timber security. Populus euphratica, one species naturally distributed in the desert area of west China, is a model for investigating the salt-tolerance mechanism in trees. In this project, we will present the whole genome bisulfite sequencing and transcriptomic sequencing for roots and leaves of P. euphratica and P. trichocarpa under control and salt stress conditions, examine the single-base resolution methylome, investigate the tissue-/species-specific variations of DNA methylation and their relationship to gene expression, and finally identify the key genes and regulation networks responsible for salt adaptation in P. euphratica. The findings will deepen our understanding of tree adaptation to salt stress and provide important genetic resources for accelerating the improvement of cultivated poplars for growth on saline soil.

土壤盐渍化是制约植物生长发育、降低农林作物产量、甚至危及生态安全的关键环境因素之一。深入研究木本植物耐盐的分子机制、进行林木遗传改良并培育抗逆新品种，对于缓解我国木材市场的供求矛盾、保障国家木材安全具有重要意义。胡杨作为我国西北干旱地区和盐碱荒漠上的高大乔木树种，是研究树木耐盐机制的最佳模式物种。本项目拟在已有工作的基础上，以胡杨及其近缘非抗逆物种毛果杨为研究材料，对盐处理和对照植株的根、叶组织进行全基因组甲基化测序和转录组测序，构建高分辨率的全基因组甲基化图谱，揭示其在盐胁迫下甲基化变异与调控模式的组织特异性和物种特异性，筛选胡杨应答盐胁迫过程中特异的、与甲基化相关的关键基因与调控网络，从表观遗传学角度解析胡杨耐盐的分子机制，为农林作物的遗传改良提供重要的基因资源。

DNA甲基化作为表观遗传修饰的重要生物形式，在植物发育和环境响应中起着关键作用。在本研究中，我们使用高通量亚硫酸氢盐测序技术，绘制了胡杨分别在正常和盐胁迫条件下的单碱基分辨率甲基化图谱。我们的数据显示，盐胁迫之后，胡杨叶组织中基因区域及其上下游2Kb、重复序列区域的甲基化水平明显升高，而在根组织中下降。我们还发现转录起始位点上游100bp的高甲基化会抑制基因表达，而基因内部和下游2kb区域的甲基化水平与基因的表达水平呈现正相关关系。在叶和根组织中我们分别鉴定出1893和1817个显著的差异甲基化区域，分别包含251和191个差异甲基化基因。这些差异甲基化基因可能通过其DNA甲基化水平的变化在胡杨响应盐胁迫的过程中发挥重要作用。这项研究从表观遗传学角度解析了胡杨耐盐的分子机制，对我们深入理解树木物种响应盐胁迫的基因调控网络提供了表观遗传学证据，进一步为开发新型甲基化分子标记用于农林作物的遗传改良、抗逆新品种的培育提供重要思路。