title: Regulation of reactive oxygen species-mediated abscisic acid signaling in guard cells and drought tolerance by glutathione.
abstract: The phytohormone abscisic acid (ABA) induces stomatal closure in response to drought stress, leading to reduction of transpirational water loss. A thiol tripeptide glutathione (GSH) is an important regulator of cellular redox homeostasis in plants. Although it has been shown that cellular redox state of guard cells controls ABA-mediated stomatal closure, roles of GSH in guard cell ABA signaling were largely unknown. Recently we demonstrated that GSH functions as a negative regulator of ABA signaling in guard cells. In this study we performed more detailed analyses to reveal how GSH regulates guard cell ABA signaling using the GSH-deficient Arabidopsis mutant cad2-1. The cad2-1 mutant exhibited reduced water loss from rosette leaves. Whole-cell current recording using patch clamp technique revealed that the cad2-1 mutation did not affect ABA regulation of S-type anion channels. We found enhanced activation of Ca(2+) permeable channels by hydrogen peroxide (H2O2) in cad2-1 guard cells. The cad2-1 mutant showed enhanced H2O2-induced stomatal closure and significant increase of ROS accumulation in whole leaves in response to ABA. Our findings provide a new understanding of guard cell ABA signaling and a new strategy to improve plant drought tolerance.
authors: Division of Agricultural and Life Science, Graduate School of Environmental and Life Science, Okayama University Okayama, Japan.
authors: Shintaro
authors: S
authors: Munemasa
authors: Daichi
authors: D
authors: Muroyama
authors: Hiroki
authors: H
authors: Nagahashi
authors: Yoshimasa
authors: Y
authors: Nakamura
authors: Izumi C
authors: IC
authors: Mori
authors: Yoshiyuki
authors: Y
authors: Murata
keywords: abscisic acid; glutathione; guard cell; reactive oxygen species; stomata