Molecular Genetics of Cell Fate Specification in the Arabidopsis Root Epidermis

多细胞生物拥有不同的细胞类型，这些细胞类型以适当的模式组织以产生功能组织和器官。发育生物学领域最大的谜团之一是定义各种细胞类型的命运和模式的机制的本质。植物是研究这一发育问题的有用生物，因为它们的许多组织是由一系列简单的细胞类型组成的，它们的细胞系可以很容易地追踪。在本项目中，开花植物拟南芥的根表皮形成被用作理解发育过程中细胞命运和模式的分子机制的模型。拟南芥根表皮细胞类型的形成是细胞位置依赖命运规范的一个非常简单而优雅的例子，这个实验系统适用于分子、遗传和细胞分析。其中一个主要优点是根表皮仅由两种细胞类型组成，即根毛细胞和无毛细胞，它们的命运取决于表皮细胞与其相邻的皮层细胞的位置关系。在最近的研究中，发现了三个基因（TTG， WER和GL2）在根表皮发育的早期阶段需要适当的细胞类型规范。本课题的研究旨在：(1)明确GL2基因在根表皮发育过程中的调控作用；(2)分析WER基因与TTG和GL2基因的关系，确定其在根表皮细胞命运中的作用；(3)利用GL2启动子融合构建物作为细胞型特异性标记基因，研究根表皮发育特征。这些研究的结果有望提供对控制拟南芥表皮细胞命运的特定基因的更好理解，以及对多细胞生物控制细胞类型多样性和模式的一般机制的新见解。

Schiefelbein 9724149 Multicellular organisms possess diverse cell types that are organized in appropriate patterns to generate functional tissues and organs. One of the great mysteries in the field of developmental biology is the nature of the mechanism that defines the fates and patterns of the various cell types. Plants are useful organisms with which to study this developmental problem because many of their tissues are composed of a simple array of cell types and their cell lineages can be traced easily. In the present project, root epidermis formation in the flowering plant Arabidopsis thaliana is used as a model for understanding the molecular mechanisms underlying cell fate and patterning during development. The formation of cell types in the Arabidopsis root epidermis is a remarkably simple and elegant example of cell position-dependent fate specification, and this experimental system is amenable to molecular, genetic, and cellular analyses. One of the major advantages is that the root epidermis is composed of only two cell types, root-hair cells and hairless cells, and their fates are determined by the positional relationship of the epidermal cells to their underlying cortical cell neighbors. In recent studies, three genes (named TTG, WER, and GL2) have been identified that are required for proper cell type specification at an early stage in root epidermis development. The research in the present project period is designed to: (1) define the regulation of the GL2 gene during root epidermis development, (2) analyze the relationship of the WER gene to the TTG and GL2 genes and determine its role in root epidermis cell fate, and (3) study the developmental features of the root epidermis by using a GL2 promoter fusion construct as a cell-type specific marker gene. The results of these studies are expected to provide a greater understanding of the specific genes controlling epidermis cell fate in Arabidopsis as well as novel insights into the general mechanisms employed by multicellular organisms to control cell-type diversity and patterning.