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  • The EMBO Journal (2007) 26, 3003 - 3014
  • doi:10.1038/sj.emboj.7601732

Published online: 31 May 2007

Rice OsHKT2;1 transporter mediates large Na+ influx component into K+-starved roots for growth

Tomoaki Horie1, Alex Costa1, Tae Houn Kim1, Min Jung Han2, Rie Horie1, Ho-Yin Leung1, Akio Miyao3, Hirohiko Hirochika3, Gynheung An2 and Julian I Schroeder1

  1. Division of Biological Sciences, Cell and Developmental Biology Section, and Center for Molecular Genetics, University of California, San Diego, La Jolla, CA, USA
  2. National Research Laboratory of Plant Functional Genomics, Department of Life Science, Pohang University of Science and Technology, Kyungbuk, Republic of Korea
  3. Division of Genome and Biodiversity Research, National Institute of Agrobiological Sciences, Ibaraki, Japan

Correspondence to:

Julian I Schroeder, Division of Biological Sciences, Cell and Developmental Biology Section, and Center for Molecular Genetics, Room 5214, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0116, USA. Tel.: +1 858 534 7759; Fax: +1 858 534 7108; E-mail: julian@biomail.ucsd.edu

Received 12 December 2006; Accepted 2 May 2007

Excessive accumulation of sodium in plants causes toxicity. No mutation that greatly diminishes sodium (Na+) influx into plant roots has been isolated. The OsHKT2;1 (previously named OsHKT1) transporter from rice functions as a relatively Na+-selective transporter in heterologous expression systems, but the in vivo function of OsHKT2;1 remains unknown. Here, we analyzed transposon-insertion rice lines disrupted in OsHKT2;1. Interestingly, three independent oshkt2;1-null alleles exhibited significantly reduced growth compared with wild-type plants under low Na+ and K+ starvation conditions. The mutant alleles accumulated less Na+, but not less K+, in roots and shoots. OsHKT2;1 was mainly expressed in the cortex and endodermis of roots. 22Na+ tracer influx experiments revealed that Na+ influx into oshkt2;1-null roots was dramatically reduced compared with wild-type plants. A rapid repression of OsHKT2;1-mediated Na+ influx and mRNA reduction were found when wild-type plants were exposed to 30 mM NaCl. These analyses demonstrate that Na+ can enhance growth of rice under K+ starvation conditions, and that OsHKT2;1 is the central transporter for nutritional Na+ uptake into K+-starved rice roots.

  • Keywords:

    • HKT,
    • Na+ uptake,
    • salt stress