VOLTAGE DEPENDENCE OF K+ CHANNELS IN GUARD-CELL PROTOPLASTS
VOLTAGE DEPENDENCE OF K+ CHANNELS IN GUARD-CELL PROTOPLASTS
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DOI：
10.1073/pnas.84.12.4108
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发表时间：
1987-06-01
影响因子：
11.1
通讯作者：
NEHER, E
中科院分区：
文献类型：
--
作者：
SCHROEDER, JI;RASCHKE, K;NEHER, E
叶片中的气孔使植物能够调节与环境的气体交换。孔孔径的变化是由周围保卫细胞中钾盐浓度的受控变化介导的。为了研究气孔运动过程中K+通量的调节，在分子水平上研究了无壁保卫细胞（原生质体）质膜上K+选择性通道的电压依赖性门控。采用全细胞膜片钳技术检测保卫细胞质膜的内向和外向K+电流。膜电位从-60 mV的保持电位去极化到比-40 mV更正的值产生外向电流，该电流被证明由K+携带。超极化引起内向K+电流。内向和外向电流对K+的选择性超过Na+，并可部分被细胞外Ba 2+所阻断。在细胞贴附和切除的膜补丁，以前确定的K+选择性单通道在保卫细胞进行了研究。电压脉冲过程中的单通道电流的平均值导致激活和失活动力学，这是类似于相应的动力学的内向和外向电流在整个细胞，表明K+-选择性通道的分子途径记录跨质膜的单保卫细胞原生质体的K+电流。估计表明，通过电压门控的K+通道记录在整个保卫细胞的K+电流可以占生理K+通量报道发生在气孔运动在叶片。
Stomatal pores in leaves enable plants to regulate the exchange of gases with their environment. Variations of the pore aperture are mediated by controlled changes of potassium salt concentrations in the surrounding guard cells. The voltage-dependent gating of K+-selective channels in the plasma membrane (plasmalemma) of cell-wall-free guard cells (protoplasts) was studied at the molecular level in order to investigate the regulation of K+ fluxes during stomatal movements. Inward and outward K+ currents across the plasmalemma of guard cells were identified by using the whole-cell configuration of the patch-clamp technique. Depolarizations of the membrane potential from a holding potential of -60 mV to values more positive than -40 mV produced outward currents that were shown to be carried by K+. Hyperpolarizations elicited inward K+ currents. Inward and outward currents were selective for K+ over Na+ and could be partially blocked by exposure to extracellular Ba2+. In cell-attached and excised membrane patches, previously identified K+-selective single channels in guard cells were studied. Averaging of single-channel currents during voltage pulses resulted in activation and deactivation kinetics that were similar to corresponding kinetics of inward and outward currents in whole cells, showing that K+-selective channels were the molecular pathways for the K+ currents recorded across the plasmalemma of single guard-cell protoplasts. Estimates demonstrate that K+ currents through the voltage-gated K+ channels recorded in whole guard cells can account for physiological K+ fluxes reported to occur during stomatal movements in leaves.