Molecular Genetics of Cell Fate Specification in the Arabidopsis Root Epidermis

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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.