Potassium-dependent changes in the expression of membrane-associated proteins in barley roots : I. Correlations with k(rb) influx and root k concentration |
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| Authors: | Fernando M Kulpa J Siddiqi M Y Glass A D |
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| Affiliation: | Department of Botany, University of British Columbia, Vancouver, B.C. V6T 2B1, Canada. |
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| Abstract: | Barley (Hordeum vulgare L. cv Halcyon) seedlings which had been grown in full strength complete inorganic nutrient media (containing 6 millimolar K+) had high internal K+ concentrations and low values of K+ (86Rb+) influx when influx was measured from solutions containing 100 micromolar K+. Transfer of these plants to solutions lacking K+ resulted in significant reductions of root and shoot K+ concentrations and values of K+ (86Rb+) influx increased by greater than 10-fold within 3 days. When plants treated in this way were returned to complete solutions, containing K+, the changes induced by K+ deprivation were reversed. Parallel studies of microsomal membranes by means of SDS-PAGE demonstrated that the expression of a group of polypeptides increased or decreased in parallel with changes of K+ (86Rb+) influx. Most prominent of these were 45 and 34 kilodalton polypeptides which specifically responded to K+ status of the barley plants; their expression was not enhanced by N or P deprivation. The 45 kilodalton polypeptide was susceptible to degradation by a membrane associated protease when microsomes were washed in buffer containing 0.2 millimolar PMSF. This loss was prevented by increasing PMSF concentration to 2 millimolar. |
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