Cellulose microfibrils provide strength to plant cell walls, as well as to the numerous commercial products made from wood and other plant fibers. Whereas cellulose provides desirable strength and durability in many applications, the biofuel industry would benefit from a supply of cellulose that is more susceptible to enzymatic or chemical breakdown. The structure and physical properties of cellulose microfibrils arise through the biosynthetic process and thus can potentially be modified. Cellulose is synthesized by membrane complexes (CSCs) that, in seed plants, consist of 24-36 cellulose synthase subunits of three different types arranged in a rosette shape. Comparative studies of algae and plants have demonstrated a relationship between CSC shape and cellulose microfibril structure. However, the factors that determine CSC shape are unknown. The CSCs of the model moss species, Physcomitrella patens, have a rosette shape like those of vascular plants, but they differ from seed plant CSCs in subunit composition. The investigators will use biochemical, genetic and molecular approaches to determine the subunit composition of the Physcomitrella patens CSCs and test specific hypotheses pertaining to their evolutionary origin. By clarifying the evolutionary history of cellulose synthase, the results of this investigation will guide efforts to determine the contributions of each of the distinct cellulose synthase types to the assembly and function of seed plant CSCs. The broader impacts of this project include training of graduate and undergraduate students, including those from underrepresented groups; development of learning modules for middle and high school students focusing on analysis and interpretation of data generated by graduate and undergraduate students; and generation of fundamental knowledge about the mechanism of cellulose biosynthesis that may contribute to efforts to genetically manipulate cellulose biosynthesis in commercial plants.
