AtHKT1 is a salt tolerance determinant that controls Na <sup>+</sup> entry into plant roots

  • Ana Rus
    Center for Plant Environmental Stress Physiology, Purdue University, West Lafayette, IN 47907-1165; Central Salt and Marine Chemicals Research Institute, Bhavanagar-364 002, India; and Department of Plant Sciences, University of Arizona, Tucson, AZ 85721
  • Shuji Yokoi
    Center for Plant Environmental Stress Physiology, Purdue University, West Lafayette, IN 47907-1165; Central Salt and Marine Chemicals Research Institute, Bhavanagar-364 002, India; and Department of Plant Sciences, University of Arizona, Tucson, AZ 85721
  • Altanbadralt Sharkhuu
    Center for Plant Environmental Stress Physiology, Purdue University, West Lafayette, IN 47907-1165; Central Salt and Marine Chemicals Research Institute, Bhavanagar-364 002, India; and Department of Plant Sciences, University of Arizona, Tucson, AZ 85721
  • Muppala Reddy
    Center for Plant Environmental Stress Physiology, Purdue University, West Lafayette, IN 47907-1165; Central Salt and Marine Chemicals Research Institute, Bhavanagar-364 002, India; and Department of Plant Sciences, University of Arizona, Tucson, AZ 85721
  • Byeong-ha Lee
    Center for Plant Environmental Stress Physiology, Purdue University, West Lafayette, IN 47907-1165; Central Salt and Marine Chemicals Research Institute, Bhavanagar-364 002, India; and Department of Plant Sciences, University of Arizona, Tucson, AZ 85721
  • Tracie K. Matsumoto
    Center for Plant Environmental Stress Physiology, Purdue University, West Lafayette, IN 47907-1165; Central Salt and Marine Chemicals Research Institute, Bhavanagar-364 002, India; and Department of Plant Sciences, University of Arizona, Tucson, AZ 85721
  • Hisashi Koiwa
    Center for Plant Environmental Stress Physiology, Purdue University, West Lafayette, IN 47907-1165; Central Salt and Marine Chemicals Research Institute, Bhavanagar-364 002, India; and Department of Plant Sciences, University of Arizona, Tucson, AZ 85721
  • Jian-Kang Zhu
    Center for Plant Environmental Stress Physiology, Purdue University, West Lafayette, IN 47907-1165; Central Salt and Marine Chemicals Research Institute, Bhavanagar-364 002, India; and Department of Plant Sciences, University of Arizona, Tucson, AZ 85721
  • Ray A. Bressan
    Center for Plant Environmental Stress Physiology, Purdue University, West Lafayette, IN 47907-1165; Central Salt and Marine Chemicals Research Institute, Bhavanagar-364 002, India; and Department of Plant Sciences, University of Arizona, Tucson, AZ 85721
  • Paul M. Hasegawa
    Center for Plant Environmental Stress Physiology, Purdue University, West Lafayette, IN 47907-1165; Central Salt and Marine Chemicals Research Institute, Bhavanagar-364 002, India; and Department of Plant Sciences, University of Arizona, Tucson, AZ 85721

抄録

<jats:p> Two <jats:italic>Arabidopsis thaliana</jats:italic> extragenic mutations that suppress NaCl hypersensitivity of the <jats:italic>sos3–1</jats:italic> mutant were identified in a screen of a T-DNA insertion population in the genetic background of Col-0 <jats:italic>gl1 sos3–1</jats:italic> . Analysis of the genome sequence in the region flanking the T-DNA left border indicated that <jats:italic>sos3–1 hkt1–1</jats:italic> and <jats:italic>sos3–1 hkt1–2</jats:italic> plants have allelic mutations in <jats:italic>AtHKT1. AtHKT1</jats:italic> mRNA is more abundant in roots than shoots of wild-type plants but is not detected in plants of either mutant, indicating that this gene is inactivated by the mutations. <jats:italic>hkt1–1</jats:italic> and <jats:italic>hkt1–2</jats:italic> mutations can suppress to an equivalent extent the Na <jats:sup>+</jats:sup> sensitivity of <jats:italic>sos3–1</jats:italic> seedlings and reduce the intracellular accumulation of this cytotoxic ion. Moreover, <jats:italic>sos3–1 hkt1–1</jats:italic> and <jats:italic>sos3–1 hkt1–2</jats:italic> seedlings are able to maintain [K <jats:sup>+</jats:sup> ] <jats:sub>int</jats:sub> in medium supplemented with NaCl and exhibit a substantially higher intracellular ratio of K <jats:sup>+</jats:sup> /Na <jats:sup>+</jats:sup> than the <jats:italic>sos3–1</jats:italic> mutant. Furthermore, the <jats:italic>hkt1</jats:italic> mutations abrogate the growth inhibition of the <jats:italic>sos3–1</jats:italic> mutant that is caused by K <jats:sup>+</jats:sup> deficiency on culture medium with low Ca <jats:sup>2+</jats:sup> (0.15 mM) and <200 μM K <jats:sup>+</jats:sup> . Interestingly, the capacity of <jats:italic>hkt1</jats:italic> mutations to suppress the Na <jats:sup>+</jats:sup> hypersensitivity of the <jats:italic>sos3–1</jats:italic> mutant is reduced substantially when seedlings are grown in medium with low Ca <jats:sup>2+</jats:sup> (0.15 mM). These results indicate that AtHKT1 is a salt tolerance determinant that controls Na <jats:sup>+</jats:sup> entry and high affinity K <jats:sup>+</jats:sup> uptake. The <jats:italic>hkt1</jats:italic> mutations have revealed the existence of another Na <jats:sup>+</jats:sup> influx system(s) whose activity is reduced by high [Ca <jats:sup>2+</jats:sup> ] <jats:sub>ext</jats:sub> . </jats:p>

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