K+ transport by the oshkt2;4 transporter from rice with atypical Na+transport properties and competition in permeation of K+over Mg2+and Ca2+Ions

Tomoaki Horie, Dennis E. Brodsky, Alex Costa, Toshiyuki Kaneko, Fiorella Lo Schiavo, Maki Katsuhara, Julian I. Schroeder

Research output: Contribution to journalArticle

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Abstract

Members of class II of the HKT transporters, which have thus far only been isolated from grasses, were found to mediate Na+-K+ cotransport and at high Na+ concentrations preferred Na+-selective transport, depending on the ionic conditions. But the physiological functions of this K+-transporting class II of HKT transporters remain unknown in plants, with the exception of the unique class II Na+ transporter OsHKT2;1. The genetically tractable rice (Oryza sativa; background Nipponbare) possesses two predicted K+-transporting class II HKT transporter genes, OsHKT2;3 and OsHKT2;4. In this study, we have characterized the ion selectivity of the class II rice HKT transporter OsHKT2;4 in yeast and Xenopus laevis oocytes. OsHKT2;4 rescued the growth defect of a K+ ptake-deficient yeast mutant. Green fluorescent protein-OsHKT2;4 is targeted to the plasma membrane in transgenic plant cells. OsHKT2;4-expressing oocytes exhibited strong K+ permeability. Interestingly, however, K+ influx in OsHKT2;4-expressing oocytes did not require stimulation by extracellular Na+, in contrast to other class II HKT transporters. Furthermore, OsHKT2;4-mediated currents exhibited permeabilities to both Mg2+ and Ca2+ in the absence of competing K+ ions. Comparative analyses of Ca2+ and Mg2+ permeabilities in several HKT transporters, including Arabidopsis thaliana HKT1;1 (AtHKT1;1), Triticum aestivum HKT2;1 (TaHKT2;1), OsHKT2;1, OsHKT2;2, and OsHKT2;4, revealed that only OsHKT2;4 and to a lesser degree TaHKT2;1 mediate Mg2+ transport. Interestingly, cation competition analyses demonstrate that the selectivity of both of these class II HKT transporters for K+ is dominant over divalent cations, suggesting that Mg2+ and Ca2+ transport via OsHKT2;4 may be small and would depend on competing K+ concentrations in plants.

Original languageEnglish
Pages (from-to)1493-1507
Number of pages15
JournalPlant Physiology
Volume156
Issue number3
DOIs
Publication statusPublished - Jul 2011

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Oocytes
transporters
Permeability
Ions
ions
calcium
rice
Triticum
Yeasts
Genetically Modified Plants
Divalent Cations
Xenopus laevis
Plant Cells
Poaceae
Green Fluorescent Proteins
Arabidopsis
permeability
oocytes
Cations
Cell Membrane

ASJC Scopus subject areas

  • Plant Science
  • Genetics
  • Physiology

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K+ transport by the oshkt2;4 transporter from rice with atypical Na+transport properties and competition in permeation of K+over Mg2+and Ca2+Ions. / Horie, Tomoaki; Brodsky, Dennis E.; Costa, Alex; Kaneko, Toshiyuki; Lo Schiavo, Fiorella; Katsuhara, Maki; Schroeder, Julian I.

In: Plant Physiology, Vol. 156, No. 3, 07.2011, p. 1493-1507.

Research output: Contribution to journalArticle

Horie, Tomoaki ; Brodsky, Dennis E. ; Costa, Alex ; Kaneko, Toshiyuki ; Lo Schiavo, Fiorella ; Katsuhara, Maki ; Schroeder, Julian I. / K+ transport by the oshkt2;4 transporter from rice with atypical Na+transport properties and competition in permeation of K+over Mg2+and Ca2+Ions. In: Plant Physiology. 2011 ; Vol. 156, No. 3. pp. 1493-1507.
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AU - Costa, Alex

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