Role of an LRR Receptor-Like Kinase in Root Epidermal Patterning

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0316312Schiefelbein During their development, all multicellular organisms generate diverse cell types and organize these cell types in appropriate patterns. The research in this project is designed to uncover the genes and the molecular mechanisms used by living things to produce and to pattern distinct cell types during development. This project uses a simple model system to study cell-type specification: the formation of the root epidermis in the flowering plant Arabidopsis thaliana. The Arabidopsis root epidermis is exceptional because its two cell types are produced in a predictable position-dependent pattern. Furthermore, the root epidermis is formed continuously as the root grows, so all stages of development can be examined at a single time. Finally, plants that lack either root epidermal cell type are viable, which enables sophisticated molecular genetic manipulations to be conducted. Recent studies suggest that cell type specification in the Arabidopsis root epidermis relies on a complex transcriptional regulatory network. Several transcription factors are produced during epidermis development, and these are involved in positive and negative feedback loops that maintain or inhibit their expression in particular cells, depending on their position. The research in this project is intended to address an important question in this system: What causes cells in one position to express these genes in a different way than cells in another position? Recently, a receptor-like protein, SCRAMBLED (SCM), has been identified that influences the position-dependent pattern of cell types. This project is designed to examine the specific role of this receptor-like SCM protein. The major aims are: (1) to define the location of the SCM mRNA and protein in the developing root, (2) to analyze the relationship between the SCM receptor function and the transcriptional regulatory network, (3) to characterize other receptor-like proteins that are similar to the SCM protein, and (4) to identify new genetic components of the SCM signaling pathway. These lines of investigation are expected to provide insights into the molecular basis for the action of positional cues during development. More generally, this will lead to a better understanding of the mechanisms employed to generate and regulate cellular diversity in multicellular organisms.