Metabolic Control of Intracellular Organic Solute Accumulation During Salt Stress

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A wide variety of plants, marine or estuarine animals, microorganisms and certain cells in the tissues of higher animals (gut, kidneys, etc.) show resistance to salt stress (highly concentrated salt solutions) by using a variety of small molecular weight, electrically neutral organic molecules as intracellular osmotic buffers. The mechanism of drought resistance is closely tied to the mechanism of salt stress resistance. Cells that cannot regulate these organic solute concentrations are not salt stress resistant. The proposed research builds on previous work and focuses on the mechanisms used by cells to regulate the intracellular concentration of these organic solutes. We propose that production and metabolic turnover of these solutes are compartmentalized within intracellular organelles such as the mitochondria and/or chloroplasts and that the rest of the cell serves as the compartment of accumulation. Using gill tissue from a highly salt stress resistant bivalve mollusc as a model system, we plan to identify the elements (enzymes) regulating production of these solutes in the mitochondria and study how the cell controls the regulation of these elements so as to adjust the internal osmotic pressure of the cell to be more or less equal to that of the media bathing cell. The research involves use of a variety of analytical chemical equipment, radiochemical tracers, some tissue culture studies, enzymatic assays and the separation of metabolic elements using various centrifugation, chromatographic, electrophoretic, and antibody precipitation techniques for specific analysis. The result will be a better understanding of the mechanisms of cellular salt stress resistance and the physiological controls regulating these processes.