First published online September 3, 2004; 10.1104/pp.104.042234
Plant Physiology 136:2500-2511 (2004)
© 2004 American Society of Plant Biologists
AtHKT1 Facilitates Na+ Homeostasis and K+ Nutrition in Planta1
Ana Rus,
Byeong-ha Lee,
Alicia Muñoz-Mayor,
Altanbadralt Sharkhuu,
Kenji Miura,
Jian-Kang Zhu2,
Ray A. Bressan and
Paul M. Hasegawa*
Center for Plant Environmental Stress Physiology, Purdue University, West Lafayette, Indiana 47907–2010 (A.R., A.S., K.M., R.A.B., P.M.H.); Department of Plant Sciences, University of Arizona, Tucson, Arizona 85721 (B.-h.L., J.-K.Z.); and Centro de Edafología y Biología Aplicada del Segura-Consejo Superior de Investigaciones Científicas, Campus Universitario de Espinardo, 30100–Murcia, Spain (A.M.-M.)
Genetic and physiological data establish that Arabidopsis AtHKT1 facilitates Na+ homeostasis in planta and by this function modulates K+ nutrient status. Mutations that disrupt AtHKT1 function suppress NaCl sensitivity of sos1-1 and sos2-2, as well as of sos3-1 seedlings grown in vitro and plants grown in controlled environmental conditions. hkt1 suppression of sos3-1 NaCl sensitivity is linked to higher Na+ content in the shoot and lower content of the ion in the root, reducing the Na+ imbalance between these organs that is caused by sos3-1. AtHKT1 transgene expression, driven by its innate promoter, increases NaCl but not LiCl or KCl sensitivity of wild-type (Col-0 gl1) or of sos3-1 seedlings. NaCl sensitivity induced by AtHKT1 transgene expression is linked to a lower K+ to Na+ ratio in the root. However, hkt1 mutations increase NaCl sensitivity of both seedlings in vitro and plants grown in controlled environmental conditions, which is correlated with a lower K+ to Na+ ratio in the shoot. These results establish that AtHKT1 is a focal determinant of Na+ homeostasis in planta, as either positive or negative modulation of its function disturbs ion status that is manifested as salt sensitivity. K+-deficient growth of sos1-1, sos2-2, and sos3-1 seedlings is suppressed completely by hkt1-1. AtHKT1 transgene expression exacerbates K+ deficiency of sos3-1 or wild-type seedlings. Together, these results indicate that AtHKT1 controls Na+ homeostasis in planta and through this function regulates K+ nutrient status.
1 This work was supported by a Spanish Government Fellowship (to A.M.-M.), by the National Institutes of Health (grant no. R01GM59138 to J.-K.Z.), and by a National Science Foundation Plant Genome Award (DBI–98–13360).
2 Present address: Botany and Plant Sciences, 2150 Bachelor Hall, University of California, Riverside, CA 92521.
Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.104.042234.
* Corresponding author; e-mail paul.m.hasegawa.1{at}purdue.edu; fax 765–494–0391.
Received March 8, 2004;
returned for revision June 3, 2004;
accepted June 4, 2004.
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