Exogenously supplied compatible solutes rapidly ameliorate NaCl-induced potassium efflux from barley roots
Exogenously supplied compatible solutes rapidly ameliorate NaCl-induced potassium efflux from barley roots
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DOI：
10.1093/pcp/pci205
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发表时间：
2005-12-01
影响因子：
4.9
通讯作者：
Shabala, S
中科院分区：
文献类型：
--
作者：
Cuin, TA;Shabala, S
研究表明，相容溶质在植物胁迫反应中的作用不仅限于常规的渗透调节，还包括一些其他的调节或渗透保护功能。在这项研究中，我们假设这样的功能之一是通过防止nacl诱导的K+从细胞中泄漏来维持细胞质K+稳态，这一特征可能赋予许多物种，特别是大麦的耐盐性。采用无创微电极离子通量（MIFE）测量技术对这一假设进行了研究。研究表明，低浓度（0.5- 5mm）的外源脯氨酸或甜菜碱显著降低了nacl诱导的大麦根部钾离子外排。这种效果是瞬时的，这意味着细胞内相容溶质的大浓度不需要改善作用。外源甜菜碱也显著增强了nacl诱导的H+外排，但仅在预孵育的根中，这表明存在其他调节机制。Sap K+和Na+分析和膜电位测量也与模型一致，即相容溶质的一个功能是通过防止nacl诱导的K+从细胞中泄漏来维持细胞质K+稳态，可能通过增强H+- atp酶的活性，控制电压依赖的外向校正K+通道，并创建二次离子运输过程所必需的电化学梯度。这些数据为离子通量通过生理上相关的低浓度相容溶质调控细胞膜提供了第一个直接证据。
It has been suggested that the role of compatible solutes in plant stress responses is not limited to conventional osmotic adjustment, but also includes some other regulatory or osmoprotective functions. In this study, we hypothesized that one such function is in maintaining cytosolic K+ homeostasis by preventing NaCl-induced K+ leakage from the cell, a feature that may confer salt tolerance in many species, particularly in barley. This hypothesis was investigated using the non-invasive microelectrode ion flux (MIFE) measuring technique. We show that low (0.5-5 mM) concentrations of exogenously supplied proline or betaine significantly reduced NaCl-induced K+ efflux from barley roots in a dose-response manner. This effect was instantaneous, implying that large intracellular concentrations of compatible solutes are not required for an amelioratory role. Exogenously supplied betaine also significantly enhanced NaCl-induced H+ efflux, but only in pre-incubated roots, implying some alternative mechanism of regulation. Sap K+ and Na+ analysis and membrane potential measurements are also consistent with the model that one function of compatible solutes is in maintaining cytosolic K+ homeostasis by preventing NaCl-induced K+ leakage from the cell, possibly through the enhanced activity of H+-ATPase, controlling voltage-dependent outward-rectifying K+ channels and creating the electrochemical gradient necessary for secondary ion transport processes. These data provide the first direct evidence for regulation of ion fluxes across the plasma membrane by physiologically relevant low concentrations of compatible solutes.