Fuchs Ines, Stölzle Sonja, Ivashikina Natalya, Hedrich Rainer
Department of Molecular Plant Physiology and Biophysics, University of Würzburg, Julius-von-Sachs-Platz 2, 97082, Würzburg, Germany.
Planta. 2005 May;221(2):212-21. doi: 10.1007/s00425-004-1437-9. Epub 2004 Dec 14.
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.
钾离子是植物吸收的最重要的大量营养元素。为了阐明模式植物水稻中钾离子吸收机制及其对盐胁迫的敏感性，我们分离并对与拟南芥根内向整流钾通道AKT1同源的水稻钾通道OsAKT1进行了功能表征。OsAKT1转录本主要存在于水稻幼苗的胚芽鞘和幼根中。在4日龄水稻幼苗的地上部和根部，钾通道mRNA均会因盐胁迫而减少。在HEK293细胞中表达后，我们能够将OsAKT1表征为一种受细胞外Ca2+和质子调控的电压依赖性内向整流钾通道。对水稻根原生质体进行的膜片钳研究鉴定出一种钾内向整流器，其通道特性与异源表达的OsAKT1相似。与盐胁迫下OsAKT1的转录下调一致，根原生质体中的内向钾电流显著降低。因此，OsAKT1似乎是水稻根中主要的盐敏感钾吸收通道。
