Potassium uptake supporting plant growth in the absence of AKT1 channel activity: Inhibition by ammonium and stimulation by sodium
| Autor: | E P, Spalding, R E, Hirsch, D R, Lewis, Z, Qi, M R, Sussman |
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| Rok vydání: | 1999 |
| Předmět: |
inorganic chemicals
Potassium Channels Arabidopsis Proteins Sodium Arabidopsis food and beverages Biological Transport plant nutrition transferred-DNA insertion mutant Rubidium root Plant Roots Article Membrane Potentials Quaternary Ammonium Compounds Mutagenesis Insertional Gene Expression Regulation Plant embryonic structures Potassium Plant Proteins |
| Zdroj: | The Journal of General Physiology |
| ISSN: | 0022-1295 |
| Popis: | A transferred-DNA insertion mutant of Arabidopsis that lacks AKT1 inward-rectifying K+ channel activity in root cells was obtained previously by a reverse-genetic strategy, enabling a dissection of the K+-uptake apparatus of the root into AKT1 and non-AKT1 components. Membrane potential measurements in root cells demonstrated that the AKT1 component of the wild-type K+ permeability was between 55 and 63% when external [K+] was between 10 and 1,000 microM, and NH4+ was absent. NH4+ specifically inhibited the non-AKT1 component, apparently by competing for K+ binding sites on the transporter(s). This inhibition by NH4+ had significant consequences for akt1 plants: K+ permeability, 86Rb+ fluxes into roots, seed germination, and seedling growth rate of the mutant were each similarly inhibited by NH4+. Wild-type plants were much more resistant to NH4+. Thus, AKT1 channels conduct the K+ influx necessary for the growth of Arabidopsis embryos and seedlings in conditions that block the non-AKT1 mechanism. In contrast to the effects of NH4+, Na+ and H+ significantly stimulated the non-AKT1 portion of the K+ permeability. Stimulation of akt1 growth rate by Na+, a predicted consequence of the previous result, was observed when external [K+] was 10 microM. Collectively, these results indicate that the AKT1 channel is an important component of the K+ uptake apparatus supporting growth, even in the "high-affinity" range of K+ concentrations. In the absence of AKT1 channel activity, an NH4+-sensitive, Na+/H+-stimulated mechanism can suffice. |
| Databáze: | OpenAIRE |
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