Cell polarity and asymmetric division in plants

描述(由申请人提供)：从有限数量的前体细胞中产生不同的后代对多细胞生物体来说是一个巨大的挑战。祖细胞在产生新细胞类型的同时需要不断更新自己；这一过程需要不对称细胞分裂(ACD)，这是干细胞的一个标志。ACD过程中的关键过程是祖细胞的细胞极化，这是由外在或内在信号启动的，最终决定了两个子细胞中不同的细胞命运。我们研究的长期目标是阐明控制ACD细胞极化和命运决定过程中协调事件的设计原则和范例。气孔的形成和形成需要ACDs的精确调控。拟南芥气孔系统为研究植物ACD的机制提供了一个很好的平台，因为这些分裂是刻板的和高度可预测的，而且暴露在空气中的叶表皮很容易获得遗传特征和细胞检查。得益于气孔系统的优势，新的蛋白质BASL(气孔谱系的断裂不对称)是在植物中发现的第一个通过其高度极化来控制ACD的内在极性蛋白质 分布在质膜上。然而，BASL极性是如何形成的，以及它是如何调节气孔ACD的，仍然是个谜。在这一应用中的中心假设是，在极性蛋白BASL和保守的MAPK途径之间的新的反馈调节在细胞极性建立和不对称细胞命运决定中发挥重要作用。这一建议的三个具体目的是：1)阐明BASL从细胞核到细胞皮质极化的分子机制；2)研究BASL和MAPK通路之间的相互依赖关系以及质膜上控制BASL极性的机制；3)建立极性蛋白如何协调植物ACD中子细胞命运的新范式。除了这一核心主题，对BASL物理伙伴和新的遗传网络的全基因组调查有望提供第一个关于植物ACD过程中内在细胞极性建立的系统控制的一瞥。目前正在研究的分子机制包括蛋白质亚细胞极化、极性蛋白质驱动的细胞命运规范以及MAPK在平衡细胞分裂和分化中的作用，这些都与人类干细胞活性和动态平衡的研究明显相关。

DESCRIPTION (provided by applicant): Generating diverse progenies from a limited number of progenitor cells is a significant challenge for multicellular organisms. The progenitor cells need to continuously renew themselves while generating new cell types; this process requires asymmetric cell divisions (ACD), a hallmark of stem cells. The key process during ACD is the cellular polarization of progenitor cells, which is initiated by either extrinsic or intrinsic cuesand eventually determines the adoption of differential cell fates in the two daughter cells. The long-term goal of our research is to elucidate the design principles and paradigms that govern the orchestrated events during cellular polarization and fate determination in ACD. The formation and patterning of stomata require precisely regulated ACDs. The Arabidopsis stomata system provides an excellent platform to study the mechanisms for ACD in plants, because these divisions are stereotypic and highly predictable, and the leaf epidermis exposed in air is readily accessible to genetic characterization and cellular examination. Benefited from the advantages of the stomatal system, the novel protein, BASL (Break Asymmetry of the Stomatal Lineages), is the first intrinsic polarity protein identified in plants that controls ACD by its highly polarized distribution at the plasma membrane. However, how BASL polarity is formed and how it regulates stomatal ACD remains elusive. The central hypothesis in this application is that a new feedback regulation between the polarity protein BASL and a conserved MAPK pathway plays an important role in cell polarity establishment and asymmetric cell fate determination. Three specific aims in this proposal are: 1) to elucidate the molecular mechanisms by which BASL is polarized from the nucleus to the cell cortex, 2) to investigate the inter-dependency between BASL and the MAPK pathway and the machineries that control BASL-based polarity at the plasma membrane, and 3) to establish a new paradigm for how polarity proteins coordinate daughter cell fates in plant ACD. Besides this core theme, the proposed genome-wide investigation of BASL physical partners and novel genetic networks promises to provide the first glimpse of the systematic control of intrinsic cell polarity establishment during ACD in plants. The molecular mechanisms under investigation involve protein subcellular polarization, polarity protein- driven cell fate specification, and MAPK functions in balancing cell division and differentiation, which are all clearly linked to the studies of human stem cell activity and homeostasis.