Functional Analysis of Vacuolar Potassium Channels

Oklahoma State University, Stillwater OK

Investigators

Abstract

Ion transport across the surrounding membrane of the central vacuole of a plant cell plays an essential role in turgor-driven movements, in intracellular signal transduction, and in plant growth and nutrition. The PI has recently identified the first vacuolar ion channel, the two-pore-domain K+ channel KCO1 of Arabidopsis thaliana. An Arabidopsis insertion mutant (kco1) lacking KCO1 was used for patch clamp analysis. Currents mediated by slow-vacuolar (SV) channels of mesophyll cell vacuoles were significantly smaller in kco1 plants compared tot the wild-type, indicating that KCO1 might be involved in the formation of SV channels. By quantitative RT-PCR it was shown that transcripts of KCO1 and KCO6 dominate in Arabidopsis mesophyll and guard cells. By a combination of reverse genetic, biophysical, and physiological approaches, the function of KCO1 and KCO6 in mesophyll and guard cells of Arabidopsis will be explored. The specific objectives are (1) to establish whether KCO6--Like KCO1--is targeted to the vacuolar membrane, (2) to identify which vacuolar ion channel is formed by KCB1 and KCO6 -- determine whether it is the SV channel or another vacuolar ion channel, and (3) to relate physiological function(s) to KCO channels. To pursue these aims, plants lacking or overexpressing KCO1 and/or KCO6 will be used. These studies will give insight into the molecular nature and physiological function of vacuolar potassium channels. This will have a major impact on plant physiology in general and on the understanding of plant growth in particular. For a systematic improvement of plant growth and nutritional composition (e.g. 'fortified foods') insight onto the molecular mechanisms of vacuolar ion transport is of vital importance. Undergraduate students, graduate students, and post-doctoral associates will be trained, and the new insights into vacuolar potassium ion transport resulting from this project will be integrated into the plant mineral nutrition and plant physiology classes given by the PI.