Identification and Characterization of Compounds that Affect Stomatal Movements

Abstract

Regulation of stomatal aperture is essential for plant growth and survival in response to environmental stimuli. Opening of stomata induces uptake of CO2 for photosynthesis and transpiration, which enhances uptake of nutrients from roots. Light is the most important stimulus for stomatal opening. Under drought stress, the plant hormone ABA induces stomatal closure to prevent water loss. However, the molecular mechanisms of stomatal movements are not fully understood. In this study, we screened chemical libraries to identify compounds that affect stomatal movements in Commelina benghalensis and characterize the underlying molecular mechanisms. We identified nine stomatal closing compounds (SCL1-SCL9) that suppress light-induced stomatal opening by >50%, and two compounds (temsirolimus and CP-100356) that induce stomatal opening in the dark. Further investigations revealed that SCL1 and SCL2 had no effect on autophosphorylation of phototropin or the activity of the inward-rectifying plasma membrane (PM) K+ channel, KAT1, but suppressed blue light-induced phosphorylation of the penultimate residue, threonine, in PM H+-ATPase, which is a key enzyme for stomatal opening. SCL1 and SCL2 had no effect on ABA-dependent responses, including seed germination and expression of ABA-induced genes. These results suggest that SCL1 and SCL2 suppress light-induced stomatal opening at least in part by inhibiting blue light-induced activation of PM H+-ATPase, but not by the ABA signaling pathway. Interestingly, spraying leaves onto dicot and monocot plants with SCL1 suppressed wilting of leaves, indicating that inhibition of stomatal opening by these compounds confers tolerance to drought stress in plants.

Coordination and trade‐offs between leaf and stem hydraulic traits and stomatal regulation along a spectrum of isohydry to anisohydry

“…Different rankings of our study species with respect to the kinetics of light‐induced stomatal opening versus VPD‐induced stomatal closure may reflect differences in the mechanisms involved. Stomatal responses to light depend on activation of plasma membrane H + ‐ATPase (Toh et al, ), sucrose degradation, and glycolysis and the tricarboxylic acid cycle (Medeiros et al, ). However, the short‐term stomatal response to VPD appears to be mediated by up‐regulation of abscisic acid biosynthesis (McAdam & Brodribb, ) or the sensitivity of ion transporters (Pantin & Blatt, ).…”

“…Stomatal responses to light depend on activation of plasma membrane H + -ATPase (Toh et al, 2018), sucrose degradation, and glycolysis and the tricarboxylic acid cycle (Medeiros et al, 2018).…”

Plant Chemical Biology

“…Since ABA is a small molecule, it would be intriguing to know if other small molecules can control this system. Here, Toh et al (2018) report a comprehensive screening of chemical libraries to identify compounds that affect stomatal movements and the underlying molecular mechanisms. They showed that stomatal closing compounds (SCLs) suppress light-induced stomatal opening, and that SCL1 and SCL2 suppress light-induced stomatal opening at least in part by inhibiting blue light-induced activation of plasma membrane H + -ATPase, which is a key enzyme for stomatal opening.…”

DeepStomata: Facial Recognition Technology for Automated Stomatal Aperture Measurement

“…Recently, we isolated compounds that regulate stomatal movements (stomatal closing compounds; SCLs) in a chemical screen focussed on stomatal apertures 9 . Limiting to include only chemicals for quantification that altered stomatal aperture greatly enhanced the screening throughput to 150 compounds per day, which resulted in the successful identification of 9 candidates from over 20,000 chemicals.…”

“…Our calculated IC 50 of ABA was close to a previously reported value, 0.36 µM 9 . Next, we reanalysed 715 images acquired from our recent chemical screen to identify compounds that alter stomatal movement 9 . In addition to the stomatal apertures, we also calculated the percentage of open, partially open, and closed stomata classified by the CNN.…”