Characterization of rice KT/HAK/KUP potassium transporters and K⁺ uptake by HAK1 from Oryza sativa Characterization of rice KT/HAK/KUP potassium transporters and K<sup>+</sup> uptake by HAK1 from <i>Oryza sativa</i>

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Abstract

<p>Plant high-affinity K<sup>+</sup> (HAK) transporters are divided into four major clusters. Cluster I transporters, in particular, are thought to have high-affinity for K<sup>+</sup>. Of the 27 <i>HAK</i> genes in rice, eight HAK transporters belong to cluster I. In this study, we investigated the temporal expression patterns during K<sup>+</sup> deficiency and K<sup>+</sup> transport activity of these eight HAK transporters. The expression of seven <i>HAK</i> genes except <i>OsHAK20</i> was detected. Expression of <i>OsHAK1</i>, <i>OsHAK5</i> and <i>OsHAK21</i> was induced in response to K<sup>+</sup> deficiency; however, that of other genes was not. Six of the eight HAK transporters—OsHAK1, OsHAK5, OsHAK19, OsHAK20, OsHAK21, and OsHAK27—complemented the K<sup>+</sup>-transporter-deficient yeast or bacterial strain. Further, the yeast cells expressing <i>OsHAK1</i> were more sensitive to Na<sup>+</sup> than those expressing <i>OsHAK5</i>. Mutant analysis showed that the high-affinity K<sup>+</sup> uptake activity was almost undetectable in <i>oshak1</i> mutants in a low-K<sup>+</sup> medium (0.02 mM). In addition, the high-affinity K<sup>+</sup> uptake activity of wild-type plants was inhibited by mild salt stress (20 mM NaCl); however, Na<sup>+</sup> permeability of OsHAK1 was not detected in <i>Escherichia coli</i> cells. The high-affinity K<sup>+</sup> uptake activity by leaf blades was detected in wild-type plants, while it was not detected in <i>oshak1</i> mutants. Our results suggest that OsHAK1 and OsHAK5 are the two important components of cluster I corresponding to low-K<sup>+</sup> conditions, and that the transport activity of OsHAK1, unlike that of OsHAK5, is sensitive to Na<sup>+</sup>. Further, <i>OsHAK1</i> is suggested to involve in foliar K<sup>+</sup> uptake.</p>

Journal

  • Plant Biotechnology

    Plant Biotechnology 35(2), 101-111, 2018

    Japanese Society for Plant Cell and Molecular Biology

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