K+ CHANNELS OF STOMATAL GUARD-CELLS - BIMODAL CONTROL OF THE K+ INWARD-RECTIFIER EVOKED BY AUXIN
K+ CHANNELS OF STOMATAL GUARD-CELLS - BIMODAL CONTROL OF THE K+ INWARD-RECTIFIER EVOKED BY AUXIN
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DOI：
10.1046/j.1365-313x.1994.5010055.x
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发表时间：
1994-01-01
期刊：
影响因子：
7.2
通讯作者：
THIEL, G
中科院分区：
文献类型：
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作者：
BLATT, MR;THIEL, G
研究了生长素吲哚-3-乙酸（IAA）和1-萘乙酸（NAA）对蚕豆气孔保护细胞K+通道的影响及其调控作用。在0.1 ~ 100 ma的IAA和NAA环境下，用多管微电极刺穿完整的保护细胞，记录细胞膜电位，并在电压箝位下监测K+通道电流。在插入后，在10 mM KCl存在的情况下，用IAA或NAA进行挑战，导致至少四种不同的电流协同调制，这些电流具有不同的动力学特征和浓度依赖性。同等浓度的苯甲酸完全不起作用。最引人注目的是，由内向整流的K+通道（I(K,in)）携带的电流对IAA和NAA都表现出双峰响应，而在洗浴介质中洗涤生长素时则相反。稳态电流在0.1 ~ 10 μ m之间增加1.3 ~ 2倍，在接近30 μ m及以上的浓度时拮抗。生长素对I（K,in）的激动作用与时间和电压无关。相比之下，在较高的生长素浓度下，I（K,in）失活表现为电压依赖性和电流激活动力学减慢。在30mm Na+-丁酸盐存在下，当细胞质pH（pH(I)）稳定在7.0附近时，生长素对I（K,in）的失活得到缓解。除了对I（K, In）的控制外，第二类（向外整流）K+通道所携带的电流在生长素浓度约为10 muM及以上时呈单调且很大程度上与电压无关的上升，IAA和NAA还激活了具有电压依赖性的保护细胞阴离子通道的内向电流。背景电流的进一步变化与H+- atp酶的有限激活一致。在检测的浓度范围内，生长素引起的膜超极化和去极化可达+/-12-19 mV，这取决于生长素添加前的自由运行膜电位。长时间暴露于100ma的生长素中超过3-5分钟，通常会引起快速转换到E(K)附近的电压以及再生动作电位。然而，在每种情况下，电压响应都是生长素作用于K+通道的可预测结果，在100毫安时，生长素作用于阴离子电流。这些结果表明生长素对K+通道活性的控制，与这些通道在调节气孔运动中K+通量的作用一致；这些数据将I（K,in）的活性与双峰特征联系起来，暗示pH(I)是其控制的假定中间物，并为生长素引发的多重信号级联提供了强有力的证据；最后，他们强调了生长素对运输活动的协调调节，从而与脱落酸的刺激-反应耦合模式进行了密切的类比。
The influence of the auxins indole-3-acetic acid (IAA) and 1-napthylene acetic acid (NAA) on K+ channels and their control was examined in stomatal guard cells of Vicia faba L. Intact guard cells were impaled with multibarrelled microelectrodes to record membrane potentials and to monitor K+ channel currents under voltage clamp during exposures to 0.1-100 muM IAA and NAA. Following impalements, challenge with either IAA or NAA in the presence of 10 mM KCl resulted in the concerted modulation of at least four different currents with distinct kinetic characteristics and concentration dependencies. Equivalent concentrations of benzoic acid were wholly without effect. Most striking, current carried by inward-rectifying K+ channels (I(K,in)) exhibited a bimodal response to both IAA and NAA which was reversed on washing the auxins from the bathing medium. The steady-state current was augmented 1.3- to 2-fold at concentrations between 0.1 and 10 muM and antagonized at concentrations near 30 muM and above. Auxin agonism Of I(K,in) was time- and voltage-independent. By contrast, I(K,in) inactivation at the higher auxin concentrations was marked by a voltage-dependence and slowing of the kinetics for current activation. Inactivation Of I(K,in) by the auxins was relieved when cytoplasmic pH (pH(i)) was clamped near 7.0 in the presence of 30 mM Na+-butyrate. In addition to the control Of I(K,in), current carried by a second class of (outward-rectifying) K+ channels rose in a monotonic and largely voltage-independent manner with auxin concentrations about 10 muM and above, and IAA and NAA also activated an inward-going current with a voltage dependence characteristic of guard cell anion channels. Further changes in background current were consistent with a limited activation of the H+-ATPase. Over the concentration range examined, the auxins evoked membrane hyperpolarizations and depolarizations of up to +/-12-19 mV, depending on the free-running membrane potential prevailing before auxin additions. Prolonging exposures to 100 muM auxin beyond 3-5 min frequently elicited rapid transitions to voltages near E(K) as well as regenerative action potentials. However, in every case the voltage response was a predictable consequence of auxin action on the K+ channels and, at 100 muM auxin, on the anion current. These results demonstrate a control of K+ channel activity by auxin, consistent with the roles of these channels in mediating K+ flux for stomatal movements; the data associate a bimodal characteristic with the activity Of I(K,in), implicating pH(i) as a putative intermediate in its control, and offer strong evidence for a multiplicity of signal cascades evoked by auxin; finally, they highlight a coordinate modulation of transport activities by auxin, thereby drawing a close analogy to the pattern of stimulus-response coupling in abscisic acid.