Molecular analysis of SCD complex function in Rab signaling in cell morphogenesis and function

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The objectives of this project are to better understand how plant cells divide and enlarge, which are key aspects of plant biology necessary for the growth and health of plants. The final step of cell division, known as cytokinesis, involves the splitting of a cell into two daughter cells and is followed by expansion of the new cells. However, many of the mechanisms involved in these processes are not well understood in either plants or animals. Specifically, this project will focus on how new membrane barriers and cell wall form between and around newly divided plant cells. The information gained has the potential to reveal new strategies for improving crop yield and quality on American farms necessary for increased food security and energy independence. In addition, young scientists at the high school, undergraduate, graduate, and postgraduate level will receive advanced research training in the areas of biochemistry, genetics and microscopy. Graduate students and postdoctoral fellows will also gain teaching and mentoring skills by supervising high school and undergraduates including underrepresented students in the UW-Madison IBS Summer Research Program. Additionally, the project will generate research tools for both the plant and the general research communities including image analysis software for the quantitative tracking of biological molecules and non-biological materials. The long-term objective of this project is to understand the molecular mechanisms involved in intracellular membrane trafficking required for plant growth and development including: cytokinesis, cell wall biosynthesis, hormone signaling, nutrient uptake, and pathogen defense. SCD1 and SCD2 encode plant-specific clathrin-coated vesicle proteins necessary for cytokinesis, cell expansion and pathogen defense. Recent studies have demonstrated that SCD1 and SCD2 are subunits of a previously uncharacterized protein complex that interacts with Rab proteins, which are central regulators of vesicle trafficking. The focus of this project is to investigate the function of this newly identified SCD complex and its regulation of Rab/clathrin-dependent membrane trafficking in dividing and non-dividing cells. The specific aims of this project are to 1) Biochemically characterize the composition and activity of the SCD complex, 2) Define effectors and regulators of the SCD/Rab complex, and 3) Develop and apply quantitative imaging approaches to analyze and describe the function of the SCD complex and its cognate Rabs in intracellular membrane trafficking necessary for plant cell morphogenesis. These studies will generate fundamental knowledge into the function of plant-specific and evolutionarily conserved membrane-trafficking proteins in plants and other eukaryotic systems.