PYR/PYL/RCAR Abscisic Acid Receptors Regulate K and Cl- Channels through Reactive Oxygen Species-Mediated Activation of Ca2 Channels at the Plasma Membrane of Intact Arabidopsis Guard Cells

作者：Wang Yizhou; Chen Zhong Hua; Zhang Ben; Hills Adrian; Blatt Michael R^*

来源：Plant Physiology, 2013, 163(2): 566-577.

DOI：10.1104/pp.113.219758

The discovery of the START family of abscisic acid (ABA) receptors places these proteins at the front of a protein kinase/phosphatase signal cascade that promotes stomatal closure. The connection of these receptors to Ca2 signals evoked by ABA has proven more difficult to resolve, although it has been implicated by studies of the pyrbactin-insensitive pyr1/pyl1/pyl2/pyl4 quadruple mutant. One difficulty is that flux through plasma membrane Ca2 channels and Ca2 release from endomembrane stores coordinately elevate cytosolic free Ca2 concentration ([Ca2 ](i)) in guard cells, and both processes are facilitated by ABA. Here, we describe a method for recording Ca2 channels at the plasma membrane of intact guard cells of Arabidopsis (Arabidopsis thaliana). We have used this method to resolve the loss of ABA-evoked Ca2 channel activity at the plasma membrane in the pyr1/pyl1/pyl2/pyl4 mutant and show the consequent suppression of [Ca2 ](i) increases in vivo. The basal activity of Ca2 channels was not affected in the mutant; raising the concentration of Ca2 outside was sufficient to promote Ca2 entry, to inactivate current carried by inward-rectifying K channels and to activate current carried by the anion channels, both of which are sensitive to [Ca2 ](i) elevations. However, the ABA-dependent increase in reactive oxygen species (ROS) was impaired. Adding the ROS hydrogen peroxide was sufficient to activate the Ca2 channels and trigger stomatal closure in the mutant. These results offer direct evidence of PYR/PYL/RCAR receptor coupling to the activation by ABA of plasma membrane Ca2 channels through ROS, thus affecting [Ca2 ](i) and its regulation of stomatal closure.

• 出版日期2013-10