Investigation of cell polarity mechanisms connected to cell fate and pattern formation in Arabidopsis vascular and stomatal development

植物是具有许多专门组织的复杂生物体。细胞多样性的重要来源是不对称分裂的干细胞，产生不同命运的子细胞。为了在植物细胞谱系中定向和执行不对称分裂，通过分子调节剂的极性定位来建立细胞极性，分子调节剂的作用模式仍然知之甚少。在这里，我将研究细胞极性蛋白如何1）调节细胞分裂和不同细胞谱系内的命运，2）在命运转换过程中以时空方式进行调节，3）组织质膜蛋白质组/蛋白质组成的亚结构域。为了解决这些长期存在的问题，我将比较两种不同但功能相互依赖的基本植物结构的发展中使用的极性机制：使气体与环境交换的气孔和在整个植物中分配水，营养物质和糖的脉管系统。我的初步数据表明，打破气孔不对称（BASL），极性蛋白和气孔谱系的基本调节器，也调节维管细胞分裂。利用遗传学和组织学方法，我将进一步研究BASL的遗传框架及其与极性局部血管调节因子（如BREVIS RADIX（BRX））的相互作用。另一个重要的未探索的方面是特定细胞类型内BASL蛋白水平的时空控制，我将使用一个强大的细胞培养系统来识别BASL降解机制的组成部分。我的第三种方法需要开拓一种新的技术，以发展植物生物学-接近标记-映射和比较质膜蛋白质组的两个不同的，极化的子域在气孔和维管谱系。使用特定的极性标记BASL-BRX和一种新的蛋白质，我确定定位相反的BRX结构域（抗BRX）结合生物素为基础的邻近标记方法成功地建立在主机实验室，把我在一个独特的位置，以确定极化质膜蛋白质组。我希望产生新的见解细胞极性和命运一般，并揭示细胞类型之间的特定差异气孔和血管的发展，特别是。由于气孔和脉管系统从根本上决定植物的适应性，因此确定调节发育的共同极性机制不仅可以成为我独立研究生涯的起点，而且还有助于提高未来的作物产量。

Plants are complex organisms with many specialized tissues. Important origins of cellular diversity are asymmetrically dividing stem cells that produce daughter cells of different fate. To orient and execute asymmetric divisions in plant cell lineages, cell polarity is established by polar localization of molecular regulators whose modes of action are still only poorly understood. Here I will investigate how cell polarity proteins 1) regulate cell division and fate within distinct cell lineages, 2) are regulated in a spatio-temporal manner during fate transitions and 3) organize subdomains of the plasma membrane proteome/protein composition. To address these long-standing issues, I will compare polarity mechanisms used in the development of two distinct, but functionally co-dependent and essential plant structures: stomata that enable gas exchange with the environment and the vasculature that distributes water, nutrients and sugars throughout the plant. My preliminary data suggests that BREAKING ASYMMETRY IN THE STOMATAL LINEAGE (BASL), a polarity protein and fundamental regulator of the stomatal lineage, also regulates vascular cell divisions. Using genetic and histological approaches, I will further investigate the genetic framework of BASL and its interaction with polar localized vascular regulators, such as BREVIS RADIX (BRX). Another important unexplored aspect is the spatio-temporal control of BASL protein levels within specific cell types, and I will use a powerful cell culture system to identify components of BASL’s degradation machinery. My third approach requires pioneering a technique new to developmental plant biology - proximity labeling - to map and compare plasma membrane proteomes of two distinct, polarized subdomains in both stomata and vascular lineages. Using specific polarity markers BASL-BRX and a new protein I identified to localize opposite of the BRX domain (anti-BRX) in combination with a biotin-based proximity labeling approach successfully established in the host lab, puts me in a unique position to determine polarized plasma membrane proteomes. I expect to generate novel insights into cell polarity and fate in general, and to reveal cell-type specific differences between stomatal and vascular development in particular. As stomata and vasculature fundamentally determine plant fitness, identifying common polarity mechanisms regulating development could not only be the starting point of my independent research career but could also help to increase crop yield in the future.