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.

Keywords: Circadian clock; Drought; Pathogen; Salinity; Temperature stress.

Fig. 1

The circadian system in higher plants

Fig. 2

The circadian oscillators regulate the diel expression of PIF4 in thermomorphogenesis

Fig. 3

MYB-like transcription factors and PRRs in the circadian clock regulate the transcription of CBFs in response to low temperatures

Fig. 4

Circadian clock gates ABA signaling in response to drought stress

Fig. 5

PRRs and GI regulate Na⁺ transport through transcription and post-transcriptional mechanisms, respectively