Circadian clock in plants: Linking timing to fitness

Abstract

Endogenous circadian clock integrates cyclic signals of environment and daily and seasonal behaviors of organisms to achieve spatiotemporal synchronization, which greatly improves genetic diversity and fitness of species. This review addresses recent studies on the plant circadian system in the field of chronobiology, covering topics on molecular mechanisms, internal and external Zeitgebers, and hierarchical regulation of physiological outputs. The architecture of the circadian clock involves the autoregulatory transcriptional feedback loops, post-translational modifications of core oscillators, and epigenetic modifications of DNA and histones. Here, light, temperature, humidity, and internal elemental nutrients are summarized to illustrate the sensitivity of the circadian clock to timing cues. In addition, the circadian clock runs cell-autonomously, driving independent circadian rhythms in various tissues. The core oscillators responds to each other with biochemical factors including calcium ions, mineral nutrients, photosynthetic products, and hormones. We describe clock components sequentially expressed during a 24-h day that regulate rhythmic growth, aging, immune response, and resistance to biotic and abiotic stresses. Notably, more data have suggested the circadian clock links chrono-culture to key agronomic traits in crops.

The circadian clock ticks in plant stress responses

“…In addition, the light intensity is inversely related to the period length of circadian rhythm, in other words, the higher the light fluence, the shorter the period length (Xu et al, 2022b). It is known that blue or red light treatment can change the period length of CAB2:LUC rhythm, and phytochromes and cryptochromes play critical roles in the entrainment of the circadian clock (Somers et al, 1998).…”

“…The circadian clock system in plants consists of time-giving input pathways mediated by environmental signals, sequentially expressed core oscillators, and numerous output pathways. The timing givers in the environment are also called "Zeitgebers", which cue time of day or season (Xu et al, 2022b). The expression of core oscillators is regulated by input signal components, and then directly or indirectly act on the rhythmic transcript accumulation of their target genes, thereby generating daily cellular, metabolic, and physiological rhythms or seasonal rhythms (Greenham and McClung, 2015;McClung, 2019;Webb et al, 2019;Sanchez et al, 2020) (Fig.…”

Nanomaterials as an alternative to increase plant resistance to abiotic stresses

“…Light from sunlight, and recently from artificial sources, is not only essential for plant growth and development through photosynthesis but also in gene expression, production of natural bioactive compounds, and synchronization of the circadian clock ( Aguirre-Becerra et al., 2020 ; Aguirre-Becerra et al., 2021 ; Xu et al., 2022 ). Light intensity, direction, quality (wavelength), and photoperiod are sensed by specialized designed proteins that sense light named photoreceptors, triggering chain reactions that have been studied in terms of photomorphogenesis and primary and secondary metabolites production ( Alvarado et al., 2019 ).…”

Phenology and Stem Growth Dynamics of Betula Pendula Roth. In the Spanish Pyrenees.

“…Tree species phenology research serves to understand the variations in the annual rhythms of trees growth and the relationship that might have with climate change since the timing of the phenological events can be considerably modi ed by warming and water stress jeopardizing growth, reproduction and the survival of trees (Chuine 2010, Xu et al 2022. In temperate and cold zones and in high mountain areas in Southern Europe, trees go through an annual cycle in which a period of growth and a dormant state in winter alternate.…”

“…) and growth arrest due to water stress (Cooke et al 2012;Mwimba et al 2018, Xu et al 2022. Other differential factors with respect to Northern Europe, such as the length of the night and daily temperature uctuations during the growth period, could also have a signi cant impact on the growth rate.…”