Discovery of the Mechanisms Enabling the Dynamic Architecture of the Plant ER

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INTELLECTUAL MERITA central question in eukaryotic cell biology is how the identity of organelles is established and maintained. The endoplasmic reticulum (ER) is an essential organelle of the secretory pathway for the production of a wide variety of the cell's building blocks, as well as for the control of essential stress and hormonal signaling pathways. To achieve maximum efficiency, the ER assumes a unique architecture characterized by a network of interconnected membrane tubules and sheets to form closed polygons. Discoveries in ER integrity are emerging from studies in various model organisms/systems such as fruit flies, yeast and cultured human cells. Compared with these systems, however, the ER has acquired unique morphological and functional features in the plant lineage that are likely linked to its important role in lipid synthesis together with chloroplast, intercellular communication, protein storage and plant-specific hormone signaling. The goal of this project is to investigate the unique regulatory mechanisms that maintain plant ER integrity by using genetic mutants, live cell imaging and biochemical approaches. These approaches have identified several genes that encode critical players involved in ER integrity and architecture including an Arabidopsis ER-associated dynamin-like protein, named RHD3. The project research aims to elucidate the mechanistic role of RHD3, as well as other gene products identified by mutant screens, in maintaining the architecture and functions of the plant ER. Since integrity and function are two inextricably linked features of the ER, the research will advance the general understanding of ER roles in the plant secretory pathway in the context of a multicellular organism and contribute to answering fundamental questions regarding differences in ER organization and function across eukaryotic systems. BROADER IMPACTSPlants are the direct or indirect primary carbon and nitrogen source of all animals and humans, in addition to their role in providing materials and fuels. The secretory pathway of plants plays a fundamental role in the conversion of fixed carbon into energy-rich materials, such as proteins, lipids and complex sugars. These plant-derived products are not only important for nutrition, but have the potential to be used as renewable fuels, lubricants, textiles and building materials. Because unique variations exist among eukaryotes as a result of evolutionary adaptation, it is important to study the unique properties of the plant ER which is the key organelle for the biosynthesis of important building blocks of cells and for essential signaling path-ways in growth, development and stress responses. The project will also broaden the impact of on the plant cell science research community by providing unique plant lines and constructs which will be made available to other plant cell biologists. The research will promote teaching, research training and outreach activities through multiple avenues both at Michigan State University as well as the local community. In particular, project personnel will continue to communicate to students and teachers discoveries in plant science and their impact on the society by engaging students and teachers in research activities in the lab and by performing science presentations at schools.