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.
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Acknowledgements
We thank D. Becker (University of Würzburg) for helpful discussions, P. Dietrich (University of Würzburg) and I. Marten (University of Würzburg) for critical reading and comments on the manuscript. We are also grateful to P. Nick (University of Karlsruhe) for providing a clone of OsARF1. This work was supported by a Körber European Science Award to R.H.
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Fuchs, I., Stölzle, S., Ivashikina, N. et al. Rice K+ uptake channel OsAKT1 is sensitive to salt stress. Planta 221, 212–221 (2005). https://doi.org/10.1007/s00425-004-1437-9
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DOI: https://doi.org/10.1007/s00425-004-1437-9