Blue Light Regulation of Stomatal Opening and the Plasma Membrane H+-ATPase

Abstract

Recent progress of the blue light signaling pathway in guard cells highlights its regulation of H⁺-ATPase activity.

Figure 1.

Blue light signaling pathway in stomatal guard cells. Arrows and a T-bar represent positive and negative regulation, respectively. The P in the white circles indicates a phosphorylation of each protein. The timescale of each peak of the key signaling events for blue light-induced stomatal opening (∼2 h) is shown as follows: phototropin activation (within 1 min), H⁺ pumping (∼2.5 min), hyperpolarization (several min), K⁺ accumulation (between 30 and 60 min). Triacylglycerol breakdown, starch degradation, and vacuolar remodeling are observed within 1 to 2 h after the start of light illumination. phot, Phototropin; 14-3-3, 14-3-3 protein; Chl., chloroplast; PAR, photosynthetically active radiation; TAG, triacylglycerol.

Figure 2.

Schematic structure of PM H⁺-ATPases. PM H⁺-ATPases possess 10 transmembrane domains (TM1 to TM10) and three cytosolic domains, including the N-terminal domain, catalytic domain, and C-terminal autoinhibitory domain containing the R-I and R-II regions (Palmgren, 2001). There are several phosphorylation sites in the C-terminal domain (Thr-881, Ser-899, Thr-924, Ser-931, and Thr-947). Thr-881, Ser-899, and Ser-931 are phosphorylated by PSY1R, FERONIA, and PKS5, respectively. The 14-3-3 protein binds to the phosphorylated penultimate Thr (Thr-947). The numbering of the amino acid residues corresponds to Arabidopsis H⁺-ATPase2.