CIRCADIAN CLOCK ASSOCIATED1 (CCA1) and the Circadian Control of Stomatal Aperture

Abstract

The endogenous circadian (;24 h) system allows plants to anticipate and adapt to daily environmental changes. Stomatal aperture is one of the many processes under circadian control; stomatal opening and closing occurs under constant conditions, even in the absence of environmental cues. To understand the significance of circadian-mediated anticipation in stomatal opening, we have generated SGC (specifically guard cell) Arabidopsis (Arabidopsis thaliana) plants in which the oscillator gene CIRCADIAN CLOCK ASSOCIATED1 (CCA1) was overexpressed under the control of the guard-cell-specific promoter, GC1. The SGC plants showed a loss of ability to open stomata in anticipation of daily dark-to-light changes and of circadian-mediated stomatal opening in constant light. We observed that under fully watered and mild drought conditions, SGC plants outperform wild type with larger leaf area and biomass. To investigate the molecular basis for circadian control of guard cell aperture, we used large-scale qRT-PCR to compare circadian oscillator gene expression in guard cells compared with the "average" whole-leaf oscillator and examined gene expression and stomatal aperture in several lines of plants with misexpressed CCA1. Our results show that the guard cell oscillator is different from the average plant oscillator. Moreover, the differences in guard cell oscillator function may be important for the correct regulation of photoperiod pathway genes that have previously been reported to control stomatal aperture. We conclude by showing that CONSTANS and FLOWERING LOCUS T, components of the photoperiod pathway that regulate flowering time, also control stomatal aperture in a daylength-dependent manner.

Daily rhythms of phytomelatonin signaling modulate diurnal stomatal closure via regulating reactive oxygen species dynamics in Arabidopsis

“…In CCA1‐ox arrhythmic plants ( CIRCADIAN CLOCK ASSOCIATED 1 ; under the cauliflower mosaic virus 35S promoter), the stomata remain open until dark‐initiated closure; in contrast, in wild‐type plants stomatal conductance already decreases in the afternoon . Additionally, CCA1 ‐overexpressing Arabidopsis under the guard cell‐specific promoter ( G C) showed a loss of circadian‐mediated stomatal opening …”

“…5 Additionally, CCA1overexpressing Arabidopsis under the guard cell-specific promoter (GC) showed a loss of circadian-mediated stomatal opening. 6 Reactive oxygen species (ROS), including superoxide (O 2 − ), hydroxyl radicals (OH − ), and hydrogen peroxide (H 2 O 2 ) were initially thought to be toxic byproducts of aerobic metabolism. To cope with the oxidative damage caused by accumulating ROS, plants have evolved the enzymatic (eg, superoxide dismutase, peroxidases, and catalase) and non-enzymatic (eg, glutathione, ascorbate, and flavonoids) ROS-scavenging antioxidant mechanisms that maintain ROS homeostasis.…”

Acclimation to Fluctuating Light Impacts the Rapidity of Response and Diurnal Rhythm of Stomatal Conductance

“…It has been recognized that the circadian clock at 126 least in part controls these diurnal modifications in A and g s responses over the diurnal 127 period (e.g. Hassidim et al, 2017), through regulating the temporal 128 patterns of transcription in photosynthesis, stomatal opening and other physiological 129 processes (Gorton et al, 1989(Gorton et al, , 1993Hubbard & Webb, 2015). Phase adjustment of the over the entire diurnal period, as these will have important implications for cumulative A 141 and water loss as well as model predictions.…”

On the move through time – a historical review of plant clock research

“…; Hassidim et al . ). Also in leaves only a weak coupling between adjacent cells has been suggested (Wenden et al .…”