Temporal Control of Plant–Environment Interactions by the Circadian Clock

Abstract

The rotation of the earth generates dramatic daily and seasonal variation in the terrestrial environment. Plants, like other organisms, have evolved an endogenous biological oscillator to predict these daily changes in light and temperature and adjust to shifting seasonal conditions. This system must be robust to unexpected environmental challenges but can also assist plants to adjust physiology accordingly. Key features of the circadian system which contribute to achieve these are the process of entrainment, by which external cues adjust the state of the oscillator, and gating, by which the sensitivity to a stimulus is modified according to the time of day. In this way, the circadian clock is a dynamic hub which integrates physiology, metabolism and growth in the context of a plant's current environment. We provide a comprehensive summary of the molecular composition of the core oscillator in Arabidopsis and the mechanisms of entrainment and gating. In particular, we focus on phytohormone signalling, photosynthetic metabolism and defense responses as examples of core plant responses to environment that are integrated within the circadian system. We are grateful for financial support from the University of Melbourne.

Superoxide is promoted by sucrose and affects amplitude of circadian rhythms in the evening

“…Circadian clocks are an endogenous timekeeping mechanism, which regulate rhythms of physiology and metabolism and control responses to environmental signals according to the time of day (6). The core circadian oscillator in Arabidopsis is a network of transcription factors composed of Myb-like genes CIRCADIAN CLOCK ASSOCIATED 1 (CCA1), LATE ELONGATED HYPOCOTYL (LHY), and REVIELLE (RVE) expressed at dawn; PSEUDO RESPONSE REGULATOR (PRR) genes expressed through the day, including TIMING OF CAB 1 (TOC1) at dusk; and the Evening Complex in the night.…”

Of clocks and coenzymes in plants: intimately connected cycles guiding central metabolism?

“…Their adaptive importance is exemplified by the fact that genetic components of clocks are widely believed to have evolved independently in biological lineages (Young & Kay, 2001). In plants and cyanobacteria, benefits occur when the genetically encoded circadian clock (referred to as ‘the clock’ from here on) is resonant with the environment, such as daily rhythms of light and temperature (Haydon et al ., 2019). Moreover, appropriate regulation by the molecular components of the clock enhances photosynthesis, biomass, seed viability, and survival in plants (Dodd et al ., 2005).…”

Combining GAL4 GFP enhancer trap with split luciferase to measure spatiotemporal promoter activity in Arabidopsis

“…The circadian clock orchestrates rhythmic gene expression according to daily environmental cues. The Arabidopsis core circadian oscillator is comprised of a gene network of regulatory feedback loops involving around 20 genes (Haydon et al , ). Although most core oscillator genes are expressed in all cells, there is spatial heterogeneity of circadian gene expression in Arabidopsis (Para et al , ; Xu et al , ; James et al , ; Wenden et al , ; Martí et al , ; Endo et al , ; Takahashi et al , ; Bordage et al , ; Kim et al , ; Gould et al , ; Greenwood et al , ).…”