Inhibition of blue light-dependent H+ pumping by abscisic acid through hydrogen peroxide-induced dephosphorylation of the plasma membrane H+-ATPase in guard cell protoplasts.
Blue light (BL)-dependent H+ pumping by guard cells, which drives stomatal opening, is inhibited by abscisic acid (ABA). We investigated this response with respect to the activity of plasma membrane H+-ATPase using Vicia guard cell protoplasts. ATP hydrolysis by the plasma membrane H+-ATPase, phosphorylation of the H+-ATPase, and the binding of 14-3-3 protein to the H+-ATPase stimulated by BL were inhibited by ABA at 10 microm. All of these responses were similarly inhibited by hydrogen peroxide (H2O2) at 1 mm. The ABA-induced inhibitions of BL-dependent H+ pumping and phosphorylation of the H+-ATPase were partially restored by ascorbate, an intracellular H2O2 scavenger. A single-cell analysis of the cytosolic H2O2 using 2',7'-dichlorofluorescin revealed that H2O2 was generated by ABA in guard cell protoplasts. We also indicated that H+ pumping induced by fusicoccin and the binding of 14-3-3 protein to the H+-ATPase were inhibited slightly (approximately 20%) by both ABA and H2O2. By contrast, H2O2 at 1 mm did not affect H+ pumping by the H+-ATPase in microsomal membranes. From these results, we concluded that inhibition of BL-dependent H+ pumping by ABA was due to a decrease in the phosphorylation levels of H+-ATPase and that H2O2 might be involved in this response. Moreover, there are at least two inhibition sites by ABA in the BL signaling pathway of guard cells.
Zhang
Xiao
X
Department of Biology, Faculty of Science, Kyushu University, Ropponmatsu, Fukuoka, Japan 810-8560.
Wang
Hengbin
H
Takemiya
Atsushi
A
Song
Chun-peng
CP
Kinoshita
Toshinori
T
Shimazaki
Ken-ichiro
K
D000040:Abscisic Acid / Q000494:pharmacology*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D008027:Light; D010766:Phosphorylation / Q000187:drug effects; D010937:Plant Growth Regulators / Q000502:physiology*; D010944:Plants / Q000378:metabolism* / Q000648:ultrastructure; D006180:Proton-Translocating ATPases / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects; D011522:Protons; D011523:Protoplasts / Q000201:enzymology; D031307:Vicia faba / Q000378:metabolism
D010937:Plant Growth Regulators; D011522:Protons; D000040:Abscisic Acid; D006861:Hydrogen Peroxide; D006180:Proton-Translocating ATPases