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.

Wang, Y., Chen, Z., Zhang, B. , Hills, A. and Blatt, M. R. (2013) 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. Plant Physiology, 163(2), pp. 566-577. (doi: 10.1104/pp.113.219758) (PMID:23899646)

Abstract

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 <i>pyr1/pyl1/pyl2/pyl4</i> 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 <i>pyr1/pyl1/pyl2/pyl4</i> 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.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Hills, Mr Adrian and Blatt, Professor Michael and Zhang, Dr Ben and Chen, Dr Zhonghua and Wang, Dr Yizhou
• Authors: Wang, Y., Chen, Z., Zhang, B., Hills, A., and Blatt, M. R.
• College/School: College of Medical Veterinary and Life Sciences > School of Molecular Biosciences
• Journal Name: Plant Physiology
• Publisher: American Society of Plant Biologists
• ISSN: 0032-0889
• ISSN (Online): 1532-2548
• Copyright Holders: Copyright © 2013 The Authors
• First Published: First published in Plant Physiology 163(2):566-577
• Publisher Policy: Reproduced under a Creative Commons License

Project Code	Award No	Project Name	Principal Investigator	Funder's Name	Funder Ref	Lead Dept
61699	1	Directed control of secretory vesicle fusion	Michael Blatt	Biotechnology and Biological Sciences Research Council (BBSRC)	BB/K015893/1	RI MOLECULAR CELL & SYSTEMS BIOLOGY