Rop GTPase Signaling Networks: Roles in Development and Stress Responses

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0115078YangGuanine nucleotide-binding proteins (G proteins) are universal molecular switches that control the flow of extracellular signals to intracellular signal transduction pathways in eukaryotic organisms. Arabidopsis possesses a unique subfamily of small G proteins, termed Rop. Rop regulates many signal transduction pathways in Arabidopsis. This proposed research is focused on a Rop-dependent pathway that controls the morphogenesis of leaf epidermal pavement cells. Because plant cells are encased in cell walls and are non-motile, cell morphogenesis is particularly important for plant growth and development. Having a unique cell shape with interlocking lobes and sinuses, epidermal pavement cells provide a useful model system for studying the mechanism of cell morphogenesis in plants. Previous studies using transgenic expression of Rop2 dominant mutant genes suggest that one or more Rops controls the formation of lobes. However, these studies did not reveal which of the 11 Arabidopsis Rop GTPases participate in the signaling pathway that controls the morphogenesis of pavement cells. Furthermore, other components in this pathway are unknown. As a first step in the long-term goal of elucidating the molecular mechanism of cell morphogenesis in Arabidopsis, this proposed work contains two major aims. First, knockout mutants for Arabidopsis Rop genes will be used to determine which Rop gene(s) controls the morphogenesis of leaf pavement cells. Second, components of the Rop-dependent morphogenesis pathway will be identified using the yeast two-hybrid method complemented with a high throughput proteomics approach. This research plan is expected to identify new genes that control cell morphogenesis and plant development. These genes may prove to be useful for genetically manipulating plant forms that are beneficial to agricultural and horticultural practices.