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Competition between uptake of ammonium and potassium in barley and Arabidopsis roots: molecular mechanisms and physiological consequences

Plants can use ammonium (NH(4)(+)) as the sole nitrogen source, but at high NH(4)(+) concentrations in the root medium, particularly in combination with a low availability of K(+), plants suffer from NH(4)(+) toxicity. To understand the role of K(+) transporters and non-selective cation channels in...

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Autores principales: Hoopen, Floor ten, Cuin, Tracey Ann, Pedas, Pai, Hegelund, Josefine N., Shabala, Sergey, Schjoerring, Jan K., Jahn, Thomas P.
Formato: Texto
Lenguaje:English
Publicado: Oxford University Press 2010
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Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2877888/
https://www.ncbi.nlm.nih.gov/pubmed/20339151
http://dx.doi.org/10.1093/jxb/erq057
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author Hoopen, Floor ten
Cuin, Tracey Ann
Pedas, Pai
Hegelund, Josefine N.
Shabala, Sergey
Schjoerring, Jan K.
Jahn, Thomas P.
author_facet Hoopen, Floor ten
Cuin, Tracey Ann
Pedas, Pai
Hegelund, Josefine N.
Shabala, Sergey
Schjoerring, Jan K.
Jahn, Thomas P.
author_sort Hoopen, Floor ten
collection PubMed
description Plants can use ammonium (NH(4)(+)) as the sole nitrogen source, but at high NH(4)(+) concentrations in the root medium, particularly in combination with a low availability of K(+), plants suffer from NH(4)(+) toxicity. To understand the role of K(+) transporters and non-selective cation channels in K(+)/NH(4)(+) interactions better, growth, NH(4)(+) and K(+) accumulation and the specific fluxes of NH(4)(+), K(+), and H(+) were examined in roots of barley (Hordeum vulgare L.) and Arabidopsis seedlings. Net fluxes of K(+) and NH(4)(+) were negatively correlated, as were their tissue concentrations, suggesting that there is direct competition during uptake. Pharmacological treatments with the K(+) transport inhibitors tetraethyl ammonium (TEA(+)) and gadolinium (Gd(3+)) reduced NH(4)(+) influx, and the addition of TEA(+) alleviated the NH(4)(+)-induced depression of root growth in germinating Arabidopsis plants. Screening of a barley root cDNA library in a yeast mutant lacking all NH(4)(+) and K(+) uptake proteins through the deletion of MEP1–3 and TRK1 and TRK2 resulted in the cloning of the barley K(+) transporter HvHKT2;1. Further analysis in yeast suggested that HvHKT2;1, AtAKT1, and AtHAK5 transported NH(4)(+), and that K(+) supplied at increasing concentrations competed with this NH(4)(+) transport. On the other hand, uptake of K(+) by AtHAK5, and to a lesser extent via HvHKT2;1 and AtAKT1, was inhibited by increasing concentrations of NH(4)(+). Together, the results of this study show that plant K(+) transporters and channels are able to transport NH(4)(+). Unregulated NH(4)(+) uptake via these transporters may contribute to NH(4)(+) toxicity at low K(+) levels, and may explain the alleviation of NH(4)(+) toxicity by K(+).
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spelling pubmed-28778882010-05-28 Competition between uptake of ammonium and potassium in barley and Arabidopsis roots: molecular mechanisms and physiological consequences Hoopen, Floor ten Cuin, Tracey Ann Pedas, Pai Hegelund, Josefine N. Shabala, Sergey Schjoerring, Jan K. Jahn, Thomas P. J Exp Bot Research Papers Plants can use ammonium (NH(4)(+)) as the sole nitrogen source, but at high NH(4)(+) concentrations in the root medium, particularly in combination with a low availability of K(+), plants suffer from NH(4)(+) toxicity. To understand the role of K(+) transporters and non-selective cation channels in K(+)/NH(4)(+) interactions better, growth, NH(4)(+) and K(+) accumulation and the specific fluxes of NH(4)(+), K(+), and H(+) were examined in roots of barley (Hordeum vulgare L.) and Arabidopsis seedlings. Net fluxes of K(+) and NH(4)(+) were negatively correlated, as were their tissue concentrations, suggesting that there is direct competition during uptake. Pharmacological treatments with the K(+) transport inhibitors tetraethyl ammonium (TEA(+)) and gadolinium (Gd(3+)) reduced NH(4)(+) influx, and the addition of TEA(+) alleviated the NH(4)(+)-induced depression of root growth in germinating Arabidopsis plants. Screening of a barley root cDNA library in a yeast mutant lacking all NH(4)(+) and K(+) uptake proteins through the deletion of MEP1–3 and TRK1 and TRK2 resulted in the cloning of the barley K(+) transporter HvHKT2;1. Further analysis in yeast suggested that HvHKT2;1, AtAKT1, and AtHAK5 transported NH(4)(+), and that K(+) supplied at increasing concentrations competed with this NH(4)(+) transport. On the other hand, uptake of K(+) by AtHAK5, and to a lesser extent via HvHKT2;1 and AtAKT1, was inhibited by increasing concentrations of NH(4)(+). Together, the results of this study show that plant K(+) transporters and channels are able to transport NH(4)(+). Unregulated NH(4)(+) uptake via these transporters may contribute to NH(4)(+) toxicity at low K(+) levels, and may explain the alleviation of NH(4)(+) toxicity by K(+). Oxford University Press 2010-05 2010-03-25 /pmc/articles/PMC2877888/ /pubmed/20339151 http://dx.doi.org/10.1093/jxb/erq057 Text en © 2010 The Author(s). This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.5), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. This paper is available online free of all access charges (see http://jxb.oxfordjournals.org/open_access.html for further details)
spellingShingle Research Papers
Hoopen, Floor ten
Cuin, Tracey Ann
Pedas, Pai
Hegelund, Josefine N.
Shabala, Sergey
Schjoerring, Jan K.
Jahn, Thomas P.
Competition between uptake of ammonium and potassium in barley and Arabidopsis roots: molecular mechanisms and physiological consequences
title Competition between uptake of ammonium and potassium in barley and Arabidopsis roots: molecular mechanisms and physiological consequences
title_full Competition between uptake of ammonium and potassium in barley and Arabidopsis roots: molecular mechanisms and physiological consequences
title_fullStr Competition between uptake of ammonium and potassium in barley and Arabidopsis roots: molecular mechanisms and physiological consequences
title_full_unstemmed Competition between uptake of ammonium and potassium in barley and Arabidopsis roots: molecular mechanisms and physiological consequences
title_short Competition between uptake of ammonium and potassium in barley and Arabidopsis roots: molecular mechanisms and physiological consequences
title_sort competition between uptake of ammonium and potassium in barley and arabidopsis roots: molecular mechanisms and physiological consequences
topic Research Papers
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2877888/
https://www.ncbi.nlm.nih.gov/pubmed/20339151
http://dx.doi.org/10.1093/jxb/erq057
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