Molecular characterization of a new protein complex in plants essential for heterochromatin silencing and genome stability.

植物通过分生组织的活动发育，分生组织含有自我更新的干细胞池，不断为所有组织和器官的形成提供新的细胞。维持这些干细胞种群对于植物的成功生长和发育是至关重要的。我们已发表的工作表明，两个基因共享一个保守的转座子相关结构域，在根尖分生组织的维持中发挥关键作用。我们将这些基因命名为分生组织维持(Main)和分生组织维持1(MAIL1)。由于DNA损伤的积累和干细胞的死亡，任何一个基因的功能丧失突变都会显示出原发的根生长停滞。此外，这些突变体显示了在所有组织中通过一种迄今未知的机制发生的转座元件编码基因子集的沉默。我们的初步结果表明，这些蛋白质可能参与了RNA加工复合体。在这个项目中，我们的目标是通过两种互补的方法来鉴定这些蛋白质的分子功能：我们将进行免疫共沉淀实验，然后进行质谱分析，以鉴定这些蛋白质在其中发挥作用的蛋白质复合体。其次，我们将进行一次抑制筛选，旨在识别导致根生长停滞的调控网络。我们的结果将揭示植物中一种迄今未知的沉默机制，这可能是基于RNA加工事件。此外，我们还将对植物在分生组织中维持基因组稳定以及在DNA损伤后支持根生长和干细胞功能重建的机制提供基本的新见解。

Plants develop through the activity of meristems, which contain pools of self-renewing stem cells that continuously provide new cells for the formation of all tissues and organs. Maintenance of these stem cell populations is essential for successful plant growth and development. Our published work has shown that two genes, which share a conserved transposon-related domain, play a crucial role in the maintenance of the root apical meristem. We named these genes MAINTENANCE of MERISTEM (MAIN) and MAINTENANCE of MERISTEMS LIKE 1 (MAIL1). Loss-of-function mutants for either gene show primary root growth arrest due to accumulation of DNA damage and cell death of stem cells. Moreover, these mutants show release of silencing of a subset of transposable element encoded genes in all tissues, which occurs by a so far unknown mechanism. Our preliminary results indicate that these proteins might be involved in an RNA processing complex. In this project we are aiming at the identification of the molecular function of these proteins by focusing on two complimentary approaches: We will perform Co-Immunoprecipitation experiments followed by mass spectrometry in order to identify the protein complex, in which these proteins act. Second, we will perform a suppressor screen aimed at the identification of the regulatory network that leads to the root growth arrest. Our results will reveal a so far unknown silencing mechanism in plants, which is probably based on RNA processing events. Moreover, we will provide fundamental new insight into the mechanisms that enable plants to maintain genome stability in meristems and to support root growth and re-establishment of stem cell function after DNA damage.