Molecular Machinery of Cell Plate Formation in Plants

Ohio State University Research Foundation -Do Not Use, Columbus OH

Investigators

Abstract

The architecture of a plant organ primarily depends primarily upon the plane of cell division. The orientation of cell division is determined during the G2 phase of the cell cycle and is followed at cytokinesis by building a cell plate in the center of the phragmoplast, a cytoskeleton held structure . The cell plate is built by the fusion of Gogi-derived vesicles but the detailed mechanism how this structure is formed and how polysaccharaide biosynthesis commences is not known. Understanding the two key events, i.e. fusion of cell plate vesicles and the activation of callose synthase, during cell plate formation is of paramount importance. The PI has earlier demonstrated that a novel dynamin-like protein, Phragmoplastin, is involved in building the cell plate. Phragmoplastin appears to generate"dumbbell-shaped" vesicle-tubule-vesicle (VTV) structures which fuse at their ends to create tubulo vesicle-network. They have isolated two proteins that interact with phragmoplastin. These are cell plate-specific callose synthase and a novel UDP-glucose transferase and have been able to purify callose synthase complex. This project is aimed at determining the precise role of Phragmoplastin by measuring its GTPase activity and its regulation by calcium ions and phospholipids. The regulation of phragmoplastin will be determined by measuring its phosphorylation state and GTPase activity during cytokinesis. They have recently cloned the gene encoding the cell plate-specific callose synthase (CalS), a key enzyme involved in building the cell plate, and will study regulation of this enzyme, including its interaction with Phragmoplastin, and UDP-glucosyl transferase (UDP-GT). The isolation of callose synthase gene has allowed them to establish that callose synthase and cellulose synthases are two separate enzymes. An understanding of the mechanism of cell plate formation may help modify the plant architecture, and may allow to regulate polysaccharide biosynthesis, including both callose and cellulose. Since cell plate formation is unique to plants, this study has potential biotechnology applications by developing herbicides with cell plate as a target to control plant growth, and modify a plant organ or plant architecture at-large to increase plant productivity. Thus this study has application in both agriculture and forest industries.