In plant cells, the process of cell division (cytokinesis) forms a cell plate at the site of separation of the two daughter cells. As cell division proceeds, the cell plate undergoes changes due to transport of new cell wall components to it (exocytosis), and to membrane recycling; both processes must be regulated temporally and spatially. The protein dynamin, as well as septin-related proteins may participate in the regulation of cell plate formation. In yeast, septin activity is regulated by a modification process where another protein molecule called SUMO (small ubiquitin-like modifiers) is attached to it. Recently, the Arabidopsis thaliana SUMO conjugating enzyme was found to interact with a cell plate-associated dynamin-related protein. Whether sumoylation plays a role in cell plate formation in plants is still not known, but can now be tested using this set of proteins. The hypothesis guiding this project is that sumoylation of plant dynamin-related proteins and septin homologs might initiate the nucleation of other target proteins at the cell plate. The objectives of the project are to identify cell plate-associated proteins that are modified with SUMO using a combination of biochemistry, molecular biology and proteomics approaches, and to elucidate the function of protein sumoylation and septin homologs in the control of cytokinesis in plants. Intellectual Merit: Sumoylation plays important roles in diverse biological processes, ranging from protein targeting to transcriptional regulation. Research into protein sumoylation in plants is just beginning. The results anticipated from this research may uncover a new function of sumoylation in the control of polar exocytosis not just in plants, but in all eukaryotic cells, and will advance our understanding on how posttranslational modifications of proteins, especially modification by sumoylation, affect cell proliferation and differentiation. Broader Impacts: This project will serve as a foundation to train undergraduates, graduate students and postdoctoral associates in the area of plant biochemistry and cell biology. Dr. Hong's laboratory will also host training of high school students and high school science teachers during the summer. This project will provide a platform for integration of research with educational responsibilities.
