DLT互作蛋白TLG1调控TLG2促进水稻粒重和耐盐性的机理研究

To keep a stable high yield even under adverse conditions is one of the permanent pursuits of crop breeding. However, it is also a great challenge due to the compensation effect between the yield and the resistance. DLT is a key gene regulating plant architecture and grain shape. In our pilot studies, we obtained TLG1 (Tolerant and Large Grain 1), a DLT-interacting protein by yeast two hybrid screening, and further identified TLG2, a candidate target gene of TLG1. TLG1 was found to be abundantly enriched on the promoter region of TLG2 to regulate its expression. Additional analyses revealed that both TLG1 and TLG2 as well as DLT are involved in regulation of both grain development and salt stress response. Importantly, TLG1 overexpression not only enhanced the grain length, grain weight, and grain yield per plant, but can also significantly improve the plant resistance to high salt treatment, suggesting its great potential in crop improvement. Based on these results, this project intends to further complete the genetic pathway utilizing multiple approaches, to analyze the relationship among the three genes, to reveal how they regulate each other and how they are able to simultaneously enhance the grain weight and stress resistance at cellular and physiological levels. Finally, we will evaluate the practical values of these genes in improving crop yield under adverse conditions. Research achievements will enhance our current understanding of the relationship between yield and resistance, and provide the feasibility for breeding rice with both high and stable yield.

高产稳产是作物育种的长久目标，但由于作物产量和抗性往往具有一定的补偿效应，如何在不利条件下保持高产是育种工作的重大挑战。DLT是控制水稻株型和粒型的关键基因。前期研究中，我们通过酵母双杂交筛选到DLT互作蛋白TLG1，并鉴定到其调控的候选靶基因TLG2，发现TLG1可富集在TLG2的启动子上调控其表达。多种分析表明TLG1和TLG2以及DLT均参与对水稻籽粒大小和高盐胁迫反应的调控，其中TLG1过表达不仅可显著增加水稻粒长粒重和单株产量，还可大大增强对高盐胁迫的抗性，具有重要的应用潜力。在此基础上，本项目将结合多种手段进一步完善这一遗传途径，深入分析三者之间的作用关系和调控机理，探索其促进水稻粒重和抗性的细胞学与生理学基础及分子机制，并评估这些组分在水稻产量和抗性改良上的应用价值。研究结果对于理解产量和抗性之间的关系并提高育种效率具有重要理论和实践意义。

作物的产量和抗性性状往往相互拮抗，持续的抗性增强通常会抑制作物生长并造成减产，高抗和高产难以兼得，然而目前对产量和抗性性状的平衡机制研究还有待深入。本项目从控制水稻株型和粒型的关键基因DLT出发，筛选到其互作蛋白TLG1。生理和遗传证据表明TLG1显著促进粒长并增强耐盐性。进一步的研究揭示了TLG1可结合到TLG2的启动子区，通过影响临近区域的表观遗传修饰水平来激活TLG2表达，从而促进了细胞分裂素从地上部分向根中的转运。TLG2显著促进粒长和耐盐性，且盐胁迫可迅速诱导植物体内的细胞分裂素空间分布变化，在地上组织中降低同时在根中增加。以上结果说明，TLG1通过表观修饰激活TLG2表达，导致细胞分裂素空间分布变化，从而增强耐盐性。本项目揭示了TLG1-TLG2遗传通路平衡粒长和抗性的分子机制，发现了优化激素空间分布同时促进产量和抗性的新途径，对作物产量和抗性的协同改良具有重要的理论和实践意义。此外，我们围绕水稻产量和抗性性状受植物激素调控的分子遗传机制，进一步系统构建了油菜素甾醇（BR）信号各组分的突变体，为各成员的功能研究奠定了材料基础；发现了BR调控水稻茎节差异伸长的新机制；揭示了BR信号组分GSK2的降解机制；阐明了细胞分裂素信号蛋白PPKL1调控籽粒大小的分子机制。