Functional Characterization of the Sucrose Binding Protein

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*** 9514410 Grimes The processes that regulate carbon allocation to various organs and the developing seed directly impact plant growth, development, and productivity. In nearly all plants, the most important translocated nutrient is sucrose and, thus, understanding the molecular biology, biochemistry, and physiology of sucrose transport is a central problem in plant biology. Sucrose, a chemically inert carbohydrate, is synthesized in the cytosol of photosynthetically active leaves and, in a process termed "phloem loading," is actively loaded into the phloem against a concentration gradient for long distance transport. After transport to sink tissues, such as the developing seed, sucrose is unloaded from the phloem into the apoplastic space and, in many plant species, transported across the plasma membrane into the sink tissue cells. It has been known that sucrose movement across the plasm membrane is a well regulated process and begins with uptake of sucrose by the sink tissue cells. With funding from the NSF, Dr. Grimes and his colleagues have demonstrated that this uptake of sucrose may be mediated by the sucrose binding protein (SBP). The intent of this research is to elucidate the basic biochemistry of sucrose transport in plants and define the mechanistic role of the SBP in sucrose uptake. This work is significant in that it will provide insight into a novel membrane transport process, and contribute to our understanding of how plants make use of photosynthetic products for their growth and development. ***