A conserved primary salt tolerance mechanism mediated by HKT transporters: a mechanism for sodium exclusion and maintenance of high K+/Na+ ratio in leaves during salinity stress



    1. Division of Biological Sciences, Cell and Developmental Biology Section, and Center for Molecular Genetics, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0116, USA and
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    Corresponding author
    1. Group of Molecular and Functional Plant Biology, Research Institute for Bioresources, Okayama University, 20-1, Chuo-2-chome, Kurashiki, Okayama 710-0046, Japan
      T. Horie. Fax: +086 434 1249; e-mail: horie@rib.okayama-u.ac.jp
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  • This manuscript is part of the special issue on Drought & Salt Stress. There should be no charge for the colour figures.

T. Horie. Fax: +086 434 1249; e-mail: horie@rib.okayama-u.ac.jp


Increasing soil salinity is a serious threat to agricultural productions worldwide in the 21st century. Several essential Na+ transporters such as AtNHX1 and AtSOS1 function in Na+ tolerance under salinity stress in plants. Recently, evidence for a new primary salt tolerance mechanism has been reported, which is mediated by a class of HKT transporters both in dicots such as Arabidopsis and monocot crops such as rice and wheat. Here we present a review on vital physiological functions of HKT transporters including AtHKT1;1 and OsHKT1;5 in preventing shoot Na+ over-accumulation by mediating Na+ exclusion from xylem vessels in the presence of a large amount of Na+ thereby protecting leaves from salinity stress. Findings of the HKT2 transporter sub-family are also updated in this review. Subjects regarding function and regulation of HKT transporters, which need to be elucidated in future research, are discussed.