The structure of plant cell wall is not known in enough detail to explain any of its biological roles in such processes as growth, disease, resistance, and maintenance of cell shape. Our lack of structural knowledge is probably due to both the complexity of the structure and the paucity of researchers working on detailed structural analysis of cell walls. Dr. Mort is proposing to continue analysis of the structure of the pectins of cotton suspension culture cell walls. The goal over the next four years is to fully characterize the primary structure of these pectins. He will characterize the rhamnogalacturonan I (RGI) region with respect to the structure of its sidechains, the distribution of acetylation in its backbone, and to what polymers RGI is attached. He will determine the size of the homogalacturonan regions in cotton pectins, the distribution of rhamnosyl residues in them, the distribution of methyl esterification in them, and the type and distribution of sidechains directly attached to the galacturonic acid residues (if they exist). He will also determine the nature of the linkage between the homogalacturonan region of pectin and RGI. When these details of the structure of cell wall pectins are known it will easier to study the complexities of the biosynthesis of pectins and the functional significance of the structural complexities of pectins, and to construct a more detailed model for the structure of dicot cell walls. It will also be easier to understand the interaction of plant pathogens with cell walls.
