Potassium Transport to Shoot Organs by SHY3/AtKUP2

University Of North Carolina At Chapel Hill, Chapel Hill NC

Investigators

Abstract

To grow, plant cells take up water so that the resulting internal turgor pressure can push against the cell wall, causing it to stretch. Water uptake depends on osmotic potential provided principally by intracellular potassium (K+) ions, and potassium transport is therefore key to plant cell growth. A mutation in the gene encoding the AtKUP2 potassium transporter of the model plant Arabidopsis thaliana causes the plants to have small cells in the stem and leaves, probably because of a decrease in potassium delivery to the shoot. This grant takes three approaches to understand the precise role of AtKUP2 in potassium movements within the plant. First, study of which cells turn on the gene encoding AtKUP2 will reveal in which tissues AtKUP2 may mediate K+ uptake. Second, examination of the subcellular localization of AtKUP2 protein in these cells will reveal whether the transporter is in the plasma membrane or in a membrane of an internal storage vacuole, and whether the protein is asymmetrically localized. Third, studies of the kinetics of movements of rubidium ions (Rb+, a convenient substitute for K+) in normal and mutant plants will address where the putative block in potassium movement may be. These experiments will reveal whether the AtKUP2 transporter acts to take up potassium in root or in shoot cells, and will lead to further studies of K+ nutrition and growth control.