Enhancement of Na+ uptake currents, time-dependent inward-rectifying K+ channel currents, and K+ channel transcripts by K+ starvation in wheat root cells
Enhancement of Na+ uptake currents, time-dependent inward-rectifying K+ channel currents, and K+ channel transcripts by K+ starvation in wheat root cells
复制标题
DOI：
10.1104/pp.122.4.1387
复制
发表时间：
2000-04-01
期刊：
影响因子：
7.4
通讯作者：
Schroeder, JI
中科院分区：
文献类型：
--
作者：
Buschmann, PH;Vaidyanathan, R;Schroeder, JI
过量的低亲和力Na+吸收对糖植物的生长是有毒的。近年来，许多研究表明，K ~+和Na ~+吸收之间的相互作用可能是决定植物耐Na ~+能力的一个关键因素。研究了K+饥饿对小麦（Triticum aestivum L.）质膜Na+和K+吸收机制的影响。用膜片钳技术记录根皮层细胞。出乎意料的是，K+饥饿的小麦幼苗被发现增加的幅度和频率的时间依赖性内向整流钾通道电流（I-K（in）+）的发生。我们研究了K+饥饿是否诱导了小麦根K-in（+）通道基因的转录。分离了一个编码小麦根K+通道同源物TaAKT 1（登录号AF 207745）的cDNA。根中TaAKT 1 mRNA水平随着培养基中K+的去除而上调。此外，K+饥饿还引起瞬时Na+电流（I-Na（+））的增强。电生理分析表明，I-K（in）+和I-Na（+）不是由相同的转运蛋白介导的，这是基于：（a）不同的激活曲线，（B）不同的时间依赖性，（c）对外部Ca 2+的不同敏感性，以及（d）不同的阳离子选择性。这些数据暗示了I-Na（+）在K+饥饿过程中的Na+吸收和胁迫中的作用，并表明K-in（+）通道可能参与了K+饥饿诱导的小麦根系K+吸收。
Excessive low-affinity Na+ uptake is toxic to the growth of glycophytic plants. Recently, several reports have suggested that the interaction between K+ and Na+ uptake might represent a key factor in determining the Na+ tolerance of plants. We investigated the effects of K+ starvation on Na+ and K+ uptake mechanisms in the plasma membrane of wheat (Triticum aestivum L.) root cortex cells using the patch-clamp technique. Unexpectedly, K+ starvation of wheat seedlings was found to enhance the magnitude and frequency of occurrence of time-dependent inward-rectifying K+ channel currents (I-K(in)+). We examined whether the transcription of a wheat root K-in(+) channel gene is induced by K+ starvation. A cDNA coding for a wheat root K+ channel homolog, TaAKT1 (accession no. AF207745), was isolated. TaAKT1 mRNA levels were up-regulated in roots in response to withdrawal of K+ from the growth medium. Furthermore, K+ starvation caused an enhancement of instantaneous Na+ currents (I-Na(+)). Electrophysiological analyses suggested that I-K(in)+ and I-Na(+) are not mediated by the same transport protein based on: (a) different activation curves, (b) different time dependencies, (c) different sensitivities to external Ca2+, and (d) different cation selectivities. These data implicate a role for I-Na(+) in Na+ uptake and stress during K+ starvation, and indicate that K-in(+) channels may contribute to K+-starvation-induced K+ uptake in wheat roots.