TOR介导的糖营养信号调控SAM活性的分子机理研究

In this century the demand for plant-based products will increase dramatically as the world population rises to over 9 billion people and industrial processes become sustainable. Plant growth and development critically depend on carbon nutrient status. Processes that especially require significant energy input are phase transitions and the initiation and outgrowth of new shoot organs, such as floral transition and lateral branches/flowers, respectively. These processes are of vital importance to plant productivity and have major impact on reproductive output and thereby yield in many crops. Most of these traits are directly linked to changes in activity and/or size of shoot apical meristems, including axillary and floral meristems. Previous research points to the importance of carbon nutrients controlling meristem activity for plant growth, development, and yield, but no systematic analyses of the mechanisms involved have been performed. Of specific interest in this context is the evolutionary highly conserved, multi-protein Target Of Rapamycin (TOR) kinase complex. The TOR complex integrates signals from different branches of nutrient sensing mechanisms, and then adjusts cell growth and proliferation accordingly. Present data strongly indicate that the TOR complex provides an important link between plant nutrient status and control of meristem activity in plants. Using an integrated natural variation and genome-wide transcriptome analysis approach we propose to uncover novel TOR signalling components that coordinate meristem function according to carbon nutrient availability. The relevance of both novel and previously identified signalling intermediates will be validated by tissue-specific (mis)expression of these components in both Arabidopsis and a crop species.

目前，全球人口持续上升，人们对植物相关产品的需求相应地增加，所以持续性提高植物产量变得重要。植物生长和发育通常依赖于碳营养水平。植物生长过程中，植物开花期的转变和新器官的起始生长需要大量的能量供给。此过程通常与植物产量相关，而产量性状又和茎端分生组织、腋生和花器官分生组织的活性和大小密切相关。研究表明，糖营养可以调控分生组织活性，从而影响植物的生长、发育和产量，但目前对其机制没有系统性的研究。另外，我们发现TOR激酶复合体的目标基因在营养感受信号机制中的多个不同的信号分支中起着非常重要的作用，调控着细胞的生长和增殖，并与分生组织活性有关。在本项目中，我们拟通过新的体系筛选自然突变体，用GWAS和传统QTL相结合的方法，鉴定新的TOR信号并与SAM活性相关的候选基因。此外我们还将利用已知营养相关信号和糖反应系统之间的联系，进一步鉴定和丰富碳的利用与植物发育之间的关系，为增加作物产量奠定基础。

利用雌二醇诱导的TOR-RNAi转基因株系，我们发现在TOR受抑制的条件下，拟南芥顶端分生组织对糖处理不敏感，表明TOR信号介导了糖激活植物顶端分生组织的活性；我们鉴定了265份拟南芥生态型材料的顶端分生组织活性对糖的响应，发现糖处理下顶端分生组织的发育状态有显著差异，存在广泛的自然变异，通过GWAS分析，在第2、第3、第4染色体鉴定到10个关联位点；将筛选出的顶端分生组织对糖不敏感的生态型CS76205与Col杂交获得F2群体，利用极端表型混池-测序法，在第三染色体的定位到一个糖激活顶端分生组织活性的位点；对雌二醇诱导的TOR-RNAi转基因株系进行EMS诱变，获得了10余个TOR抑制子突变体，采用Mut-map方法克隆了其中的一个突变体，并通过CRISPR/Cas9方法，验证了HOS15是该突变体的TOR抑制子。