Journal of Plant Physiology 171 (2014) 723–731
Contents lists available at ScienceDirect
Journal of Plant Physiology journal homepage: www.elsevier.com/locate/jplph
Physiology
The twins K+ and Na+ in plants夽 ˜ Benito a,1 , Rosario Haro a,1 , Anna Amtmann b , Tracey Ann Cuin c , Ingo Dreyer a,∗ Begona a
Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid, Madrid, Spain Institute of Molecular, Cellular and Systems Biology (MCSB), College of Medical, Veterinary and Life Sciences (MVLS), University of Glasgow, Glasgow, UK c Biochimie et Physiologie Moléculaire des Plantes, Institut de Biologie Intégrative des Plantes, UMR 5004 CNRS/UMR 0386 INRA/Montpellier SupAgro/Université Montpellier 2, Montpellier, France b
a r t i c l e
i n f o
Article history: Received 26 July 2013 Received in revised form 1 October 2013 Accepted 2 October 2013 Available online 3 March 2014 Keywords: HKT Potassium Sodium Transport mechanism
a b s t r a c t In the earth’s crust and in seawater, K+ and Na+ are by far the most available monovalent inorganic cations. Physico-chemically, K+ and Na+ are very similar, but K+ is widely used by plants whereas Na+ can easily reach toxic levels. Indeed, salinity is one of the major and growing threats to agricultural production. In this article, we outline the fundamental bases for the differences between Na+ and K+ . We present the foundation of transporter selectivity and summarize findings on transporters of the HKT type, which are reported to transport Na+ and/or Na+ and K+ , and may play a central role in Na+ utilization and detoxification in plants. Based on the structural differences in the hydration shells of K+ and Na+ , and by comparison with sodium channels, we present an ad hoc mechanistic model that can account for ion permeation through HKTs. © 2013 Elsevier GmbH. All rights reserved.
Introduction Potassium with ∼2.1% (position 8) and sodium with ∼2.4% (position 6) are among the top ten elements present in the continental crust (position 1: oxygen 47.2%, 2: silicon 28.8%, 3: aluminum 8.0%, 4: iron 4.3%, 5: calcium 3.9%, 7: magnesium 2.2%, 9: titanium 0.4%, and 10: carbon 0.2%; Wedepohl, 1995). They are both far more abundant than the other alkali metals rubidium, lithium, and cesium (all
Contents lists available at ScienceDirect
Journal of Plant Physiology journal homepage: www.elsevier.com/locate/jplph
Physiology
The twins K+ and Na+ in plants夽 ˜ Benito a,1 , Rosario Haro a,1 , Anna Amtmann b , Tracey Ann Cuin c , Ingo Dreyer a,∗ Begona a
Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid, Madrid, Spain Institute of Molecular, Cellular and Systems Biology (MCSB), College of Medical, Veterinary and Life Sciences (MVLS), University of Glasgow, Glasgow, UK c Biochimie et Physiologie Moléculaire des Plantes, Institut de Biologie Intégrative des Plantes, UMR 5004 CNRS/UMR 0386 INRA/Montpellier SupAgro/Université Montpellier 2, Montpellier, France b
a r t i c l e
i n f o
Article history: Received 26 July 2013 Received in revised form 1 October 2013 Accepted 2 October 2013 Available online 3 March 2014 Keywords: HKT Potassium Sodium Transport mechanism
a b s t r a c t In the earth’s crust and in seawater, K+ and Na+ are by far the most available monovalent inorganic cations. Physico-chemically, K+ and Na+ are very similar, but K+ is widely used by plants whereas Na+ can easily reach toxic levels. Indeed, salinity is one of the major and growing threats to agricultural production. In this article, we outline the fundamental bases for the differences between Na+ and K+ . We present the foundation of transporter selectivity and summarize findings on transporters of the HKT type, which are reported to transport Na+ and/or Na+ and K+ , and may play a central role in Na+ utilization and detoxification in plants. Based on the structural differences in the hydration shells of K+ and Na+ , and by comparison with sodium channels, we present an ad hoc mechanistic model that can account for ion permeation through HKTs. © 2013 Elsevier GmbH. All rights reserved.
Introduction Potassium with ∼2.1% (position 8) and sodium with ∼2.4% (position 6) are among the top ten elements present in the continental crust (position 1: oxygen 47.2%, 2: silicon 28.8%, 3: aluminum 8.0%, 4: iron 4.3%, 5: calcium 3.9%, 7: magnesium 2.2%, 9: titanium 0.4%, and 10: carbon 0.2%; Wedepohl, 1995). They are both far more abundant than the other alkali metals rubidium, lithium, and cesium (all
