Negative regulation of abscisic acid-induced stomatal closure by glutathione in Arabidopsis
2011
Okuma, Eiji | Jahan, Md Sarwar | Munemasa, Shintaro | Hossain, Mohammad Anowar | Muroyama, Daichi | Islam, Mohammad Mahbub | Ogawa, Ken’ichi | Watanabe-Sugimoto, Megumi | Nakamura, Yoshimasa | Shimoishi, Yasuaki | Mori, Izumi C. | Murata, Yoshiyuki
We found that glutathione (GSH) is involved in abscisic acid (ABA)-induced stomatal closure. Regulation of ABA signaling by GSH in guard cells was investigated using an Arabidopsis mutant, cad2-1, that is deficient in the first GSH biosynthesis enzyme, γ-glutamylcysteine synthetase, and a GSH-decreasing chemical, 1-chloro-2,4-dinitrobenzene (CDNB). Glutathione contents in guard cells decreased along with ABA-induced stomatal closure. Decreasing GSH by both the cad2-1 mutation and CDNB treatment enhanced ABA-induced stomatal closure. Glutathione monoethyl ester (GSHmee) restored the GSH level in cad2-1 guard cells and complemented the stomatal phenotype of the mutant. Depletion of GSH did not significantly increase ABA-induced production of reactive oxygen species in guard cells and GSH did not affect either activation of plasma membrane Ca²⁺-permeable channel currents by ABA or oscillation of the cytosolic free Ca²⁺ concentration induced by ABA. These results indicate that GSH negatively modulates a signal component other than ROS production and Ca²⁺ oscillation in ABA signal pathway of Arabidopsis guard cells.
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