US-Switzerland Cooperative Research on Intracellular Location of Sucrose: Sucrose Fructosyl Transferase

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This award supports Professors Thomas Housley and Nicholas Carpita of Purdue University to collaborate in plant biochemistry research with Professor Philippe Matile and others of the University of Zurich. These scientists share an interest in the synthesis and degradation of fructans and other carbohydrates and the physiological role of these storage polymers. The focus of their collaboration is a study of the intracellular location of sucrose fructosyl transferase (SST) in leaf mesophyll cells of wheat and tuber cells of Jerusalem artichoke. They hypothesize that SST is associated with the tonoplast, the delimiting membrane of the vacuole, and facilitates transport of sucrose into the vacuole. Further, SST can dissociate from the tonoplast and that dissociation alters SST activity. They plan to test these hypotheses empirically after isolation of intact vacuoles. Dr. Matile offers expertise in the isolation of pure, intact vacuoles from higher plants. He and his research group have demonstrated convincingly that fructans, SST, and other enzymes of fructan metabolism were solely in the vacuole. Drs. Housley and Carpita offer expertise in fructan metabolism and carbohydrate structure analysis. They have demonstrated that there are two separate pools of sucrose in the cell, and that SST occupies a location in the cell where it can discriminate between these pools. Vacuoles provide a unique system to study in vitro the regulation of enzyme activity by membrane association. The proposed collaboration will use vacuoles to test a model of fructan synthesis and thus contribute insights into the kinetics of sugar incorporation in fructans of protoplasts and vacuoles. Such information is important for understanding primary productivity in plants, and is essential if we are to consider modifying plants to improve primary productivity.