Abstract：
Although there has been long-standing recognition that stimuli-induced cytosolic pH alterations coincide with changes in calcium ion (Ca2+) levels, the interdependence between protons (H+) and Ca2+ remains poorly understood. We addressed this topic using the light-gated channelrhodopsin HcKCR2 from the pseudofungus Hyphochytrium catenoides, which operates as a H+ conductive, Ca2+ impermeable ion channel on the plasma membrane of plant cells. Light activation of HcKCR2 in Arabidopsis guard cells evokes a transient cytoplasmic acidification that sparks Ca2+ release from the endoplasmic reticulum. A H+-induced cytosolic Ca2+ signal results in membrane depolarization through the activation of Ca2+-dependent SLAC1/SLAH3 anion channels, which enabled us to remotely control stomatal movement. Our study suggests a H+-induced Ca2+ release mechanism in plant cells and establishes HcKCR2 as a tool to dissect the molecular basis of plant intracellular pH and Ca2+ signaling.
摘要：
尽管长期以来一直认识到刺激诱导的细胞溶质pH值改变与钙离子（Ca2）水平的变化一致，质子（H）和Ca2之间的相互依存关系仍然知之甚少。我们使用来自假真菌的光门控通道视紫红质HcKCR2解决了这个问题，作为一个H+导电，植物细胞质膜上的Ca2+不透性离子通道。拟南芥守卫细胞中HcKCR2的光激活会引起短暂的细胞质酸化，从而激发内质网释放Ca2。H+诱导的胞浆Ca2+信号通过激活Ca2+依赖性SLAC1/SLAH3阴离子通道导致膜去极化，这使我们能够远程控制气孔运动。我们的研究提出了植物细胞中H诱导的Ca2释放机制，并建立了HcKCR2作为剖析植物细胞内pH和Ca2信号传导的分子基础的工具。
