Effect of potassium deficiency on the plasma membrane H+-ATPase of the wood ray parenchyma in poplar |
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Authors: | M. AREND,G. MONSHAUSEN,C. WIND,M. H. WEISENSEEL,& J. FROMM |
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Affiliation: | Fachgebiet Angewandte Holzbiologie, Technische Universität München, Germany and;Botanisches Institut, Universität Karlsruhe (TH), Germany |
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Abstract: | The effect of K+ deficiency on the plasma membrane (PM) H+‐ATPase was studied in young stems of poplar plants (Populus tremula × tremuloides) grown with low or full‐strength K+ supply. Immunological assays using different antibodies were applied to test if K+ deficiency affects the amount of immunodetectable PM H+‐ATPases in the stem tissue. The monoclonal antibody clone 46 E5 B11 revealed an increased abundance of PM H+‐ATPases under conditions of low K+ supply, and immunolabelling experiments showed that this increase was restricted to vessel‐associated cells (VACs) of the wood ray parenchyma. Replacement of the monoclonal antibody by a polyclonal antibody against PM H+‐ATPase gave a specific immunoreactivity on blots as well as tissue sections too, but the labelling intensity showed no difference between plants with low or full‐strength K+ supply. Measurements of extracellular H+ concentrations using non‐invasive, H+‐selective microelectrodes revealed a lowering of the pH at the surface of VACs and an enhancement of net efflux of H+ in plants grown with low K+ supply. The present results indicate an up‐regulation of specific isoforms of the PM H+‐ATPase in VACs under K+‐deficient conditions and suggest a key role for these PM H+‐ATPases in unloading K+ from the xylem stream. |
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Keywords: | H+ fluxes plasma membrane H+-ATPase potassium vessel-associated cells |
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