The long-term goal of this project is to understand how plant cells achieve various shapes. Cell shape formation is important for the development and the morphogenesis of plants, but the molecular mechanism underlying this fundamental process is poorly understood. This project focuses on a network of regulatory proteins in the control of interlocking jigsaw puzzle appearance of Arabidopsis leaf epidermal cells. A central player in this network is a plant-specific guanine nucleotide binding protein known as ROP. The formation of jigsaw puzzle appearance requires the coordination of localized cellular outgrowth in the lobe-forming region of the cell with localized constraint of outgrowth in the other regions. ROP promotes lobing by activating the RIC4 protein to assemble the actin cytoskeleton required for localized cell outgrowth, as well as by inactivating the RIC1 protein that organizes the microtubule cytoskeleton for constraining cellular outgrowth. The RIC1 pathway feedback represses ROP activation to assure the formation of indentations. In this proposed work, genetic, molecular, cell biological, and proteomic approaches will be used to elucidate the mechanism by which ROP activity is regulated as well as the mechanism underpinning the RIC1 regulation of microtubules. This research aim is expected to provide new insights into the mechanism for cell shape formation in plants and 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. This project will also integrate research with training of undergraduate and graduate students and participation of underrepresented undergraduate students through outreach programs such as Minority Student Summer Research Internships and REU Programs.
