This $1.7 million project grant from the National Science Foundation's Biological Sciences program (CFDA 47.074) will fund research at the University of Wisconsin-Madison on the regulation of exocytic membrane trafficking required for cytokinesis and polarized cell expansion in plants. Specifically, the research will focus on understanding how delivery of materials needed for plasma membrane formation and maintenance is controlled in dividing and expanding plant cells. The project aims to define the biochemical activity and regulation of the Stromal Cytokinesis Defective (SCD) complex, which is essential for this membrane trafficking process in plants. It will also delineate protein-protein and protein-lipid interactions governing SCD complex assembly and membrane association required for exocytic trafficking. Comparative studies of SCD complex homologs in Arabidopsis thaliana and Physcomitrella patens are further expected to provide insights into conserved and divergent functions across plant species. Outcomes include fundamental new knowledge about exocytic membrane trafficking mechanisms in plants and other eukaryotes.