Journal Article

A Ca<sup>2+</sup>-Sensitive System Mediates Low-Affinity K<sup>+</sup> Uptake in the Absence of AKT1 in Arabidopsis Plants

Fernando Caballero, María A. Botella, Lourdes Rubio, José A. Fernández, Vicente Martínez and Francisco Rubio

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 53, issue 12, pages 2047-2059
Published in print December 2012 | ISSN: 0032-0781
Published online October 2012 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcs140
A Ca2+-Sensitive System Mediates Low-Affinity K+ Uptake in the Absence of AKT1 in Arabidopsis Plants

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  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry

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K+ acquisition by Arabidopsis roots is mainly mediated by the high-affinity K+ transporter AtHAK5 and the inward-rectifier K+ channel AtAKT1. This model is probably universal to plants. Mutant plants lacking these two systems (athak5,atakt1) take up K+ and grow when the external K+ concentration is above a certain level, indicating that an additional transport system may compensate for the absence of AtHAK5 and AtAKT1. Here we describe that this alternative system is essential for providing sufficient K+ to sustain growth of athak5,atakt1 plants. This system is especially sensitive to Ca2+, Mg2+, Ba2+ and La3+, it transports Cs+ and its activity is reduced by cyclic nucleotides. These results suggest that a Ca2+-permeable voltage-independent non-selective cation channel, probably belonging to the cyclic nucleotide gated channel (CNGC) family, may provide the pathway for K+ uptake in athak5,atakt1 plants. The genes encoding the two members of the CNGC family that have been described as mediating root K+ uptake, AtCNGC3 and AtCNGC10, are not up-regulated in athak5,atakt1 plants, excluding overexpression of these genes as a compensatory mechanism. On the other hand, an increased driving force for K+ in athak5,atakt1 plants due to a hyperpolarization of the membrane potential of its root cells is also discarded. The identification of this unknown system may provide tools to improve plant K+ nutrition in conditions where AtAKT1 functionality is reduced, such as under salinity. In addition, this system may constitute an important pathway for accumulation of toxic cations such as Cs+ or radiocesium (137Cs+), and could play a role in phytoremediation.

Keywords: AKT1; Arabidopsis; Calcium; Cesium; Potassium; Salinity

Journal Article.  9263 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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