The circadian clock ticks in plant stress responses

Abstract

The circadian clock, a time-keeping mechanism, drives nearly 24-h self-sustaining rhythms at the physiological, cellular, and molecular levels, keeping them synchronized with the cyclic changes of environmental signals. The plant clock is sensitive to external and internal stress signals that act as timing cues to influence the circadian rhythms through input pathways of the circadian clock system. In order to cope with environmental stresses, many core oscillators are involved in defense while maintaining daily growth in various ways. Recent studies have shown that a hierarchical multi-oscillator network orchestrates the defense through rhythmic accumulation of gene transcripts, alternative splicing of mRNA precursors, modification and turnover of proteins, subcellular localization, stimuli-induced phase separation, and long-distance transport of proteins. This review summarizes the essential role of circadian core oscillators in response to stresses in Arabidopsis thaliana and crops, including daily and seasonal abiotic stresses (low or high temperature, drought, high salinity, and nutrition deficiency) and biotic stresses (pathogens and herbivorous insects). By integrating time-keeping mechanisms, circadian rhythms and stress resistance, we provide a temporal perspective for scientists to better understand plant environmental adaptation and breed high-quality crop germplasm for agricultural production.

Transcriptomic comparison sheds new light on regulatory networks for dimorphic flower development in response to photoperiod in Viola prionantha

“…Co-expression of VprGI and defense response genes indicates that these stressresponse genes might be controlled by VprGI or other circadian clock genes in V. prionantha. The circadian clock genes respond to various abiotic and biotic stressors in A. thaliana and crops [61], and Arabidopsis GI is involved in signaling pathways for various abiotic stressors [62,63]. For example, the EEL (ENHANCED EM LEVEL)-GI complex positively regulates diurnal ABA synthesis by affecting the expression of NCED3 (9-CIS-EPOXYCAROTENOID DIOXYGENASE 3) and contributes to drought tolerance in Arabidopsis [63].…”

Identification and expression of functionally conserved circadian clock genes in lichen-forming fungi

“…The circadian clock provides fitness and performance advantages in a variety of model systems, further supporting its role in environmental adaptation. In plants, the circadian clock aligns chemical defenses to herbivore feeding patterns, regulates drought responses, and anticipates pathogen attack (see Xu et al 2022 17 for a recent review of the role of the circadian clock in plant biotic and abiotic stress responses). In fungi, the asexual reproductive patterns of Neurospora crassa have long been observed to be regulated by the circadian clock 18 , 19 , while strains of Neurospora discreta with habitat-specific circadian rhythms maintain higher fitness in their respective habitats 20 .The interacting circadian clocks in symbiotic systems are a growing topic of interest 21 , 22 .…”

SOS1 safeguards plant circadian rhythm against daily salt fluctuations

“…Strikingly, a study on plant transcriptome changes in response to salt, osmotic, and cold stresses suggests that 68% of the circadian oscillatory genes are involved in stress responses ( 4 ). It is now increasingly clear that the plant circadian clock plays an indispensable role in diverse plant stress responses ( 5 ). In PNAS, Cha et al.…”

“…While the plant circadian clock has an extensive impact on plant responses to salt stress, salt stress may also have feedback regulations on the circadian clock, as the bidirectional interplays between the plant circadian clock and various environmental factors are well-known. A diverse array of environmental Zeitgebers (aka time-givers) of plant circadian clock have been discovered including sugars like glucose and fructose, inorganic nitrogen like KNO 3 and NH 4 NO 3 , nitrogen assimilation products like glutamate and glutamine, and mineral elements like iron and magnesium ( 5 ). Further considering the diurnal oscillation of transpiration rate, the endogenous Na + concentration is likely to display a diurnal difference.…”