Alleviation of rapid, futile ammonium cycling at the plasma membrane by potassium reveals K+-sensitive and -insensitive components of NH4+ transport

Journal of Experimental Botany
Mark W SzczerbaHerbert J Kronzucker

Abstract

Futile plasma membrane cycling of ammonium (NH4+) is characteristic of low-affinity NH4+ transport, and has been proposed to be a critical factor in NH4+ toxicity. Using unidirectional flux analysis with the positron-emitting tracer 13N in intact seedlings of barley (Hordeum vulgare L.), it is shown that rapid, futile NH4+ cycling is alleviated by elevated K+ supply, and that low-affinity NH4+ transport is mediated by a K+-sensitive component, and by a second component that is independent of K+. At low external [K+] (0.1 mM), NH4+ influx (at an external [NH4+] of 10 mM) of 92 micromol g(-1) h(-1) was observed, with an efflux:influx ratio of 0.75, indicative of rapid, futile NH4+ cycling. Elevating K+ supply into the low-affinity K+ transport range (1.5-40 mM) reduced both influx and efflux of NH4+ by as much as 75%, and substantially reduced the efflux:influx ratio. The reduction of NH4+ fluxes was achieved rapidly upon exposure to elevated K+, within 1 min for influx and within 5 min for efflux. The channel inhibitor La3+ decreased high-capacity NH4+ influx only at low K+ concentrations, suggesting that the K+-sensitive component of NH4+ influx may be mediated by non-selective cation channels. Using respiratory measurements an...Continue Reading

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Citations

Dec 7, 2010·Plant Cell Reports·Takushi Hachiya, Ko Noguchi
Jul 26, 2008·Journal of Experimental Botany·Mark W SzczerbaHerbert J Kronzucker
Sep 29, 2011·Journal of Experimental Botany·Devrim CoskunHerbert J Kronzucker
Apr 19, 2011·Annual Review of Plant Biology·Yi-Fang TsayShan-Hua Lin
Dec 1, 2015·Plant Signaling & Behavior·Guangjie LiWeiming Shi
Feb 17, 2009·Journal of Plant Physiology·Mark W SzczerbaHerbert J Kronzucker
Mar 4, 2008·Physiologia Plantarum·Dev T Britto, Herbert J Kronzucker
Feb 15, 2013·The Plant Journal : for Cell and Molecular Biology·Shyam K MasakapalliR George Ratcliffe
Sep 10, 2010·Plant, Cell & Environment·Daria BlochShaul Yalovsky
Sep 29, 2009·Plant, Cell & Environment·Konstantine D BalkosHerbert J Kronzucker
May 10, 2013·Plant Signaling & Behavior·Devrim Coskun, Herbert J Kronzucker
Jan 8, 2015·Frontiers in Plant Science·Lingan KongHuawei Li
May 18, 2016·Plant Science : an International Journal of Experimental Plant Biology·Raquel EstebanJose Fernando Moran
Mar 25, 2020·Journal of Experimental Botany·Huimin FengGuohua Xu
Nov 3, 2015·Plant, Cell & Environment·Devrim CoskunHerbert J Kronzucker
Oct 28, 2019·Plants·Marek SustrEdita Tylova
Aug 30, 2017·Frontiers in Plant Science·Anna PodgórskaBożena Szal
Jan 29, 2019·Journal of Experimental Botany·Guangjie LiWeiming Shi
Feb 16, 2021·Frontiers in Plant Science·María Begoña González-MoroIzargi Vega-Mas
May 26, 2021·Journal of Plant Physiology·Dev T BrittoHerbert J Kronzucker
Sep 11, 2021·Plant, Cell & Environment·Haifei ChenZhenhua Zhang

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