Plant Cell Wall Cellulose - Simple Polymer, Complexed Biosynthesis

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Plants possess an inherent plasticity in their ability to allocate carbon, which is pivotal to the effective modulation of growth and development. Moreover, plants have developed a complex regulatory system to optimize carbon assimilation within an array of dynamic environmental stimuli that is key to shaping their fitness and survival. Across species, it has been shown that there is an evolutionarily conserved relationship between leaf photosynthetic capacity and biomass investment in leaf area. Given that source tissue (i.e., mature leaves) governs the availability of carbohydrates essential for plant development, it is fair to postulate that the products of primary metabolism are therefore intricately involved in mediating plant growth and development. Sucrose is central to metabolism and is the dominant metabolite produced via photosynthesis, and in vascular plants the most commonly translocated metabolite that ultimately provides carbon for a variety of biosynthetic reactions. Among the many cellular processes that draw on these carbon skeletons, cell wall biosynthesis is a significant sink and culminates in a terminal product. The resulting chemistry and ultrastructure of the cell walls defines the physiology of the plant and, importantly, impacts form, function and fitness. The long-term objectives of the Mansfield research program is to understand the complex fundamental processes that govern carbon allocation in plants, using poplar trees (Populus spp.) and Arabidopsis as model species, with a specific emphasis on the intricacies of the biosynthetic processes governing carbohydrate metabolism and plant cell wall development. This information is key to understanding programmed cellular growth patterns, and the complex network and regulatory frameworks fundamental to xylem development (secondary cell walls). The proposed research builds on previous Discovery Grants that formed the foundations of the hypotheses to be tested. Specifically, this proposed research program is comprised of a series of experiments aimed at addressing the following questions: 1) What is the source of UDP-glucose during active cellulose deposition? 2) What role do “accessory” enzymes have in cellulose biosynthesis? 3) How is sucrose homeostasis maintained in sink tissues? A greater understanding of the molecular underpinnings of resource allocation, and the intricacies of plant secondary cell wall biosynthesis will contribute, not only to our knowledge gaps in fundamental plant biology, but also could facilitate strategies for breeding and/or engineering plants to maximize resource allocation and combat a changing climate.