Intellectual merit. Xyloglucan, a hemicellulose, is a major component of the primary cell wall of many plants and provides important structural and physiological functions. With the exception of cellulose, xyloglucan is the best characterized cell wall polysaccharide, and considerable progress has been made to identify and characterize the enzymes involved in its synthesis. Recently, six Golgi-localized transferase enzymes were shown to be involved in xyloglucan formation. However, the functional organization and regulation of these enzymes in the Golgi membrane is currently unknown. Preliminary research for this project found distinct hierarchal roles among three of the enzymes and demonstrated that all six interact in pair-wise fashion with each other. The scientific goal of this project is to define the structural organization and functional regulation of this multi-enzyme complex during the synthesis of xyloglucan in the plant cell in the model species, Arabidopsis thaliana. Research results will help to establish the mechanistic basis for the functional organization of the polysaccharide biosynthetic machinery localized in the Golgi complex of this and other plant species.
Broader Impacts. The outcome of the project will facilitate the engineering of plants to produce hemicelluloses with modified properties that will enhance development and protection against environmental stress, and will increase industrial interest in the use of plant polysaccharides. This research will be accomplished in collaboration with Michigan State University and University of California at Riverside. The collaboration will create broad opportunities and an outstanding environment for undergraduate and graduate students to be trained through a combined program of biochemistry, cell, and molecular biology. Undergraduate students will be recruited through the Iowa State University Summer Undergraduate Research Programs and the Program for Women in Science and Engineering. A six-week summer research experience will be provided for one intern each year. The project will also include a collaboration with the Iowa State University Extension to convey scientific information on plant biomass composition, formation, and modification to local biomass growers, land managers and the general public through participation in annual workshops and the creation of an internet webpage.