title: Complexity of potassium acquisition: how much flows through channels?
abstract: The involvement of potassium (K(+))-selective, Shaker-type channels, particularly AKT1, in primary K(+) acquisition in roots of higher plants has long been of interest, particularly in the context of low-affinity K(+) uptake, at high K(+) concentrations, as well as uptake from low-K(+) media under ammonium (NH₄(+)) stress. We recently demonstrated that K(+) channels cannot mediate K(+) acquisition in roots of intact barley (Hordeum vulgare L.) seedlings at low (22.5 µM) external K(+) concentrations ([K(+)](ext)) and in the presence of high (10 mM) external NH₄(+), while the model species Arabidopsis thaliana L. utilizes channels under comparable conditions. However, when external NH₄(+) was suddenly withdrawn, a thermodynamic shift to passive (channel-mediated) K(+) influx was observed in barley and both species demonstrated immediate and dramatic stimulations in K(+) influx, illustrating a hitherto unexplored magnitude and rapidity of K(+)-uptake capacity and plasticity. Here, we expand on our previous work by offering further characterization of channel-mediated K(+) fluxes in intact barley, with particular focus on anion effects, root respiration and pharmacological sensitivity and highlight key additions to the current model of K(+) acquisition.
authors: Department of Biological Sciences; University of Toronto; Toronto, ON Canada.
authors: Devrim
authors: D
authors: Coskun
authors: Herbert J
authors: HJ
authors: Kronzucker
mesh_terms: D001467:Hordeum / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism*; D018517:Plant Roots / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000378:metabolism*
chemical_list: D010940:Plant Proteins; D015221:Potassium Channels; D011188:Potassium
keywords: Arabidopsis; ammonium; anion; barley; influx; radiotracer; respiration; roots; transporters
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