A BLUS1 kinase signal and a decrease in intercellular CO2 concentration are necessary for stomatal opening in response to blue light. Issue 5 (1st March 2021)

• Record Type: Journal Article
• Authors: Hosotani, Sakurako; Yamauchi, Shota; Kobayashi, Haruki; Fuji, Saashia; Koya, Shigekazu; Shimazaki, Ken-ichiro; Takemiya, Atsushi
• Is Part Of: The Plant Cell. Volume 33:Issue 5(2021)
• Page Start: 1813
• Page End: 1827
• Publication Date: 2021-03-01
• DOI: 10.1093/plcell/koab067
• Languages: English
• ISSNs: 1040-4651

Abstract

Abstract: Light-induced stomatal opening stimulates CO2 uptake and transpiration in plants. Weak blue light under strong red light effectively induces stomatal opening. Blue light-dependent stomatal opening initiates light perception by phototropins, and the signal is transmitted to a plasma membrane H + -ATPase in guard cells via BLUE LIGHT SIGNALING 1 (BLUS1) kinase. However, it is unclear how BLUS1 transmits the signal to H + -ATPase. Here, we characterized BLUS1 signaling in Arabidopsis thaliana, and showed that the BLUS1 C-terminus acts as an auto-inhibitory domain and that phototropin-mediated Ser-348 phosphorylation within the domain removes auto-inhibition. C-Terminal truncation and phospho-mimic Ser-348 mutation caused H + -ATPase activation in the dark, but did not elicit stomatal opening. Unexpectedly, the plants exhibited stomatal opening under strong red light and stomatal closure under weak blue light. A decrease in intercellular CO2 concentration via red light-driven photosynthesis together with H + -ATPase activation caused stomatal opening. Furthermore, phototropins caused H + -ATPase dephosphorylation in guard cells expressing constitutive signaling variants of BLUS1 in response to blue light, possibly for fine-tuning stomatal opening. Overall, our findings provide mechanistic insights into the blue light regulation of stomatal opening. Abstract : BLUE LIGHT SIGNALING 1-mediated H + -ATPase activation and a decrease in intercellular CO2 concentration via red light-driven photosynthesis are required for blue light-dependent stomatal opening.