Transcriptional and Post-Translational Regulation of Plant Vacuolar Na+/H+ Antiports

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Environmental stress due to salinity is one of the most serious factors limiting the productivity of agricultural crops, which are predominantly sensitive to the presence of high concentrations of salts in the soil. A comparison of ion distribution in cells and tissues of various plant species indicates that a primary characteristic of salt tolerant plants is their ability to exclude sodium out of the cell and to take up sodium and to sequester it in the cell vacuoles. Dr. Blumwald's work has identified a family of vacuolar Na+/H+ antiports that play a paramount role in the ability of plants to grow in high NaCl concentrations. These antiports actively move ions into the vacuole, removing the potentially harmful ions from the cytosol. These ions, in turn, act as an osmoticum within the vacuole, which then maintain water flow into the cell, thus allowing plants to grow in soils containing high salinity. The cloning of plant Na+/H+ antiports and the generation of transgenic Arabidopsis thaliana plants with enhanced salt tolerance provides a unique opportunity to study the role of these transporters in salt tolerance and ion homeostasis in vivo. Dr. Blumwald's proposed research aims to identify and characterize proteins regulating the vacuolar Na+/H+ antiport activity, providing insights on the role of Ca2+-dependent transduction processes in the regulation of intracellular ion balance. The second objective will serve to identify mechanisms regulating the transcription of the antiports in salt tolerant plants that could be used to design crops with enhanced salt tolerance. The third objective, will use knockout mutants and RNA interference to determine the physiological role of the vacuolar antiports in K+ nutrition.