Faculty of Natural Sciences, Institute of Biology, Biotechnology and Environmental Protection, University of Silesia in Katowice, 40-032 Katowice, Poland.
Int J Mol Sci. 2020 Jul 10;21(14):4876. doi: 10.3390/ijms21144876.
In contrast to the well-studied effect of auxin on the plasma membrane K channel activity, little is known about the role of this hormone in regulating the vacuolar K channels. Here, the patch-clamp technique was used to investigate the effect of auxin (IAA) on the fast-activating vacuolar (FV) channels. It was found that the macroscopic currents displayed instantaneous currents, which at the positive potentials were about three-fold greater compared to the one at the negative potentials. When auxin was added to the bath solution at a final concentration of 1 µM, it increased the outward currents by about 60%, but did not change the inward currents. The imposition of a ten-fold vacuole-to-cytosol KCl gradient stimulated the efflux of K from the vacuole into the cytosol and reduced the K current in the opposite direction. The addition of IAA to the bath solution with the 10/100 KCl gradient decreased the outward current and increased the inward current. Luminal auxin reduced both the outward and inward current by approximately 25% compared to the control. The single channel recordings demonstrated that cytosolic auxin changed the open probability of the FV channels at the positive voltages to a moderate extent, while it significantly increased the amplitudes of the single channel outward currents and the number of open channels. At the positive voltages, auxin did not change the unitary conductance of the single channels. We suggest that auxin regulates the activity of the fast-activating vacuolar (FV) channels, thereby causing changes of the K fluxes across the vacuolar membrane. This mechanism might serve to tightly adjust the volume of the vacuole during plant cell expansion.
与生长素对质膜钾通道活性的研究相比，人们对这种激素在调节液泡钾通道方面的作用知之甚少。在这里，我们使用膜片钳技术研究了生长素（IAA）对快速激活液泡（FV）通道的作用。结果发现，宏观电流呈现瞬时电流，在正电位下比负电位下大约大三倍。当生长素终浓度为 1 µM 时加入浴液，它使外向电流增加约 60%，但不改变内向电流。施加十倍的液泡-细胞质 KCl 浓度梯度刺激钾从液泡流出到细胞质，从而减少相反方向的钾电流。将 IAA 加入具有 10/100 KCl 梯度的浴液中，会降低外向电流并增加内向电流。与对照相比，腔室内生长素将外向和内向电流分别降低了约 25%。单通道记录表明，胞质生长素在正电压下适度改变 FV 通道的开放概率，同时显著增加单通道外向电流的幅度和开放通道的数量。在正电压下，生长素不改变单通道的单位电导。我们认为，生长素调节快速激活液泡（FV）通道的活性，从而导致跨液泡膜钾流的变化。这种机制可能有助于在植物细胞扩张过程中紧密调节液泡的体积。
