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Planta. 2005 May;221(2):212-21. Epub 2004 Dec 14.

Rice K+ uptake channel OsAKT1 is sensitive to salt stress.

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  • 1Department of Molecular Plant Physiology and Biophysics, University of Würzburg, Julius-von-Sachs-Platz 2, 97082, Würzburg, Germany. ifuchs@botanik.uni-wuerzburg.de

Abstract

Potassium ions constitute the most important macronutrients taken up by plants. To unravel the mechanisms of K+ uptake and its sensitivity to salt stress in the model plant rice, we isolated and functionally characterized OsAKT1, a potassium channel homologous to the Arabidopsis root inward rectifier AKT1. OsAKT1 transcripts were predominantly found in the coleoptile and in the roots of young rice seedlings. K+ channel mRNA decreases in response to salt stress, both in the shoot and in the root of 4-day-old rice seedlings. Following expression in HEK293 cells, we were able to characterize OsAKT1 as a voltage-dependent, inward-rectifying K+ channel regulated by extracellular Ca2+ and protons. Patch-clamp studies on rice root protoplasts identified a K+ inward rectifier with similar channel properties as heterologously expressed OsAKT1. In line with the transcriptional downregulation of OsAKT1 in response to salt stress, inward K+ currents were significantly reduced in root protoplasts. Thus, OsAKT1 seems to represent the dominant salt-sensitive K+ uptake channel in rice roots.

PMID:
15599592
[PubMed - indexed for MEDLINE]
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