Regulatory Role of Circadian Clocks on ABA Production and Signaling, Stomatal Responses, and Water-Use Efficiency under Water-Deficit Conditions

Abstract

Plants deploy molecular, physiological, and anatomical adaptations to cope with long-term water-deficit exposure, and some of these processes are controlled by circadian clocks. Circadian clocks are endogenous timekeepers that autonomously modulate biological systems over the course of the day–night cycle. Plants’ responses to water deficiency vary with the time of the day. Opening and closing of stomata, which control water loss from plants, have diurnal responses based on the humidity level in the rhizosphere and the air surrounding the leaves. Abscisic acid (ABA), the main phytohormone modulating the stomatal response to water availability, is regulated by circadian clocks. The molecular mechanism of the plant’s circadian clock for regulating stress responses is composed not only of transcriptional but also posttranscriptional regulatory networks. Despite the importance of regulatory impact of circadian clock systems on ABA production and signaling, which is reflected in stomatal responses and as a consequence influences the drought tolerance response of the plants, the interrelationship between circadian clock, ABA homeostasis, and signaling and water-deficit responses has to date not been clearly described. In this review, we hypothesized that the circadian clock through ABA directs plants to modulate their responses and feedback mechanisms to ensure survival and to enhance their fitness under drought conditions. Different regulatory pathways and challenges in circadian-based rhythms and the possible adaptive advantage through them are also discussed.

Plants’ Physio-Biochemical and Phyto-Hormonal Responses to Alleviate the Adverse Effects of Drought Stress: A Comprehensive Review

“…Plant drought pathways use ABA as a primary stress sensor to improve the plant's response to desiccation. The rise in ABA concentration coincided with the accumulation of lycopene and carotene in the fruits [238,239].…”

Interplay among photoreceptors determines the strategy of coping with excess light in tomato

“…Management of light energy use and distribution within photosynthetic apparatus are fundamental aspects of photosynthesis regulation (Foyer et al, 2017). Light perception plays an important role in the adaption of photosynthetic organisms to the prevailing lighting environment through fine-tuning of the circadian clock (Yari Kamrani et al, 2022) or other signaling networks (Allorent & Petroutsos, 2017). Nevertheless, the role of photoreceptors in the regulation of plant's response to excess light is poorly investigated (Demarsy et al, 2018).…”

PIF transcriptional regulators are required for rhythmic stomatal movements

“…ABA likely prevents KAT1 accumulation at this time through post-transcriptional mechanisms such as KAT1 endocytosis and sequestration 21 . In the morning, a reduction in ABA is necessary for light-induced stomata opening 53 , by means of light-induced depletion of endogenous bioactive ABA through inactivation and catabolism coupled with a reduction in ABA biosynthesis 22,54 . In the absence of ABA, KAT1 accumulates and light-induced phototropin-mediated guard cell membrane hyperpolarization leads to KAT1 activation and GC opening.…”