拟南芥去泛素化酶UBP15/SOD2通过影响组蛋白H2B泛素化水平调控种子和器官大小的分子机理研究

The de-ubiquitinase UBP15/SOD2 serves as a regulator of cell proliferation to control seed and organ size, however, the molecular mechanisms of UBP15/SOD2 in regulating cell proliferation are largely unknown. The results of our previous work indicated that UBP15/SOD2 protein stability is negatively regulated by DA1, another seed and organ size regulator, and it acts downstream of DA1 to regulate organ size by promoting cell proliferation. As the UBP15/SOD2 encodes a plant de-ubiquitinase, we analyze the ubiquitin-modification of histones and found that it affects the ubiquitinated level of H2B, which is involved in gene expression regulation. In this proposal, a combination of genetic, molecular biological, cytological and biochemical methods will be used to study the mechanisms of H2B deubiquitination-modification by UBP15/SOD2 and the DNA methylation and expression regulation of the cell cycle-related genes, to screen UBP15/SOD2-interacting proteins, and to identify suppressors of UBP15/SOD2. These studies will reveal the molecular mechanisms of DA1-UBP15/SOD2 in organ size control by influencing H2B ubiquitination level, and provide the theoretical basis for gene exploring and application in yield improvement.

拟南芥去泛素化酶编码基因UBP15/SOD2功能缺失后细胞增殖受到抑制，但UBP15/SOD2参与细胞增殖调控的具体机制尚不清楚。UBP15/SOD2作用于泛素受体编码基因DA1的下游调控种子和器官大小。同时我们发现UBP15/SOD2基因参与了组蛋白H2B泛素化水平的调控，这意味着UBP15/SOD2基因很可能通过调控组蛋白H2B的泛素化水平来影响细胞增殖相关基因的表达。为了深入了解UBP15/SOD2对种子和器官大小的调控机制，本项目拟综合利用遗传学、细胞生物学、分子生物学等技术，分析UBP15/SOD2基因对组蛋白H2B泛素化水平的调控及其导致的相关基因表达调控变化、并筛选UBP15/SOD2下游调控基因及其相互作用蛋白。上述工作的开展将有助于深入了解UBP15/SOD2基因调控细胞增殖和器官大小的分子机制，为作物高产育种提供理论基础和新的基因资源。

器官大小调控是植物发育过程中的重要事件，同时也是改良农作物、提高产量的重要途径。本项目前期分离了一个调控种子大小的基因UBP15/SOD2，并阐明了DA1-UBP15/SOD2途径在调控器官和种子大小方面的作用机制。在此基础上，继续围绕UBP15/SOD2和器官大小调控，开展植物器官发育方面的研究。研究内容包括：阐明UBP15/SOD2与H2B泛素化水平的关系及在调控器官发育的作用，筛选新的调控器官发育的因子，尤其是UBP15/SOD2下游的作用因子。经过阶段性研究，目前已经基本阐明UBP15/SOD2通过影响H2B泛素化水平来调控器官发育相关基因的分子机制，筛选得到若干个相关的器官发育调控因子。对其中一个基因PDM2的研究结果表明，PDM2影响器官发育的原因是影响了叶绿体的发育，进一步分析表明，PDM2影响了质体编码多聚酶依赖的叶绿体基因转录水平显著下降，同时，也参与调控质体基因RNA的编辑效率。这些结果揭示了PDM2通过影响叶绿体发育，最终影响器官发育的基本机制。