Picking out parallels: plant circadian clocks in context

Molecular models have been described for the circadian clocks of representatives of several different taxa. Much of the work on the plant circadian system has been carried out using the thale cress, Arabidopsis thaliana , as a model. We discuss the roles of genes implicated in the plant circadian system, with special emphasis on Arabidopsis . Plants have an endogenous clock that regulates many aspects of circadian and photoperiodic behaviour. Despite the discovery of components that resemble those involved in the clocks of animals or fungi, no coherent model of the plant clock has yet been proposed. In this review, we aim to provide an overview of studies of the Arabidopsis circadian system. We shall compare these with results from different taxa and discuss them in the context of what is known about clocks in other organisms.

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Genetic interactions between clock mutations in Neurospora crassa : can they help us to understand complexity?

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2001.0967 ◽

2001 ◽

Vol 356 (1415) ◽

pp. 1717-1724 ◽

Cited By ~ 15

Author(s):

Louis W. Morgan ◽

Jerry F. Feldman ◽

Deborah Bell-Pedersen

Keyword(s):

Coupled Oscillators ◽

Temperature Compensation ◽

White Collar ◽

Circadian System ◽

Genetic Interactions ◽

Circadian Clocks ◽

Metabolic Effects ◽

Clock Model ◽

Number Of Genes ◽

Single Oscillator

Recent work on circadian clocks in Neurospora has primarily focused on the frequency ( frq ) and white–collar ( wc ) loci. However, a number of other genes are known that affect either the period or temperature compensation of the rhythm. These include the period (no relationship to the period gene of Drosophila ) genes and a number of genes that affect cellular metabolism. How these other loci fit into the circadian system is not known, and metabolic effects on the clock are typically not considered in single–oscillator models. Recent evidence has pointed to multiple oscillators in Neurospora , at least one of which is predicted to incorporate metabolic processes. Here, the Neurospora clock–affecting mutations will be reviewed and their genetic interactions discussed in the context of a more complex clock model involving two coupled oscillators: a FRQ/WC–based oscillator and a ‘ frq –less’ oscillator that may involve metabolic components.

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Timing metabolism in cartilage and bone: links between circadian clocks and tissue homeostasis

Journal of Endocrinology ◽

10.1530/joe-19-0256 ◽

2019 ◽

Vol 243 (3) ◽

pp. R29-R46 ◽

Cited By ~ 2

Author(s):

Cátia F Gonçalves ◽

Qing-Jun Meng

Keyword(s):

Rheumatoid Arthritis ◽

Circadian Rhythms ◽

Circadian System ◽

Tissue Homeostasis ◽

Circadian Clocks ◽

Clock System ◽

Metabolic Functions ◽

Biochemical Mechanisms ◽

Skeletal Disorders ◽

Bone Physiology

The circadian system in mammals is responsible for the temporal coordination of multiple physiological and behavioural processes that are necessary for homeostasis. In the skeleton, it has long been known that metabolic functions of chondrocytes, osteoblasts and osteoclasts exhibit intrinsic circadian rhythms. In addition, results from animal models reveal a close connection between the disruption of circadian rhythms and skeletal disorders such as rheumatoid arthritis, osteoarthritis and osteoporosis. In this review, we summarise the latest insights into the genetic and biochemical mechanisms linking cartilage and bone physiology to the circadian clock system. We also discuss how this knowledge can be utilised to improve human health.

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Modeling circadian clocks: From equations to oscillations

Open Life Sciences ◽

10.2478/s11535-011-0061-5 ◽

2011 ◽

Vol 6 (5) ◽

pp. 699-711 ◽

Cited By ~ 9

Author(s):

Didier Gonze

Keyword(s):

Genetic Network ◽

Cellular Level ◽

Circadian Clocks ◽

Subsequent Paper ◽

Molecular Models ◽

Response Curves ◽

Sustained Oscillations ◽

Higher Eukaryotes ◽

The Right ◽

Selection Of

AbstractCircadian rhythms are generated at the cellular level by a small but tightly regulated genetic network. In higher eukaryotes, interlocked transcriptional-translational feedback loops form the core of this network, which ensures the activation of the right genes (proteins) at the right time of the day. Understanding how such a complex molecular network can generate robust, self-sustained oscillations and accurately responds to signals from the environment (such as light and temperature) is greatly helped by mathematical modeling. In the present paper we review some mathematical models for circadian clocks, ranging from abstract, phenomenological models to the most detailed molecular models. We explain how the equations are derived, highlighting the challenges for the modelers, and how the models are analyzed. We show how to compute bifurcation diagrams, entrainment, and phase response curves. In the subsequent paper, we discuss, through a selection of examples, how modeling efforts have contributed to a better understanding of the dynamics of the circadian regulatory network.

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Adaptive diversification in the cellular circadian behavior of Arabidopsis leaf- and root-derived cells

10.1101/2021.06.10.447857 ◽

2021 ◽

Author(s):

Shunji Nakamura ◽

Tokitaka Oyama

Keyword(s):

Environmental Changes ◽

Cell Types ◽

Cellular Level ◽

Circadian System ◽

Circadian Clocks ◽

Intrinsic Properties ◽

Adaptive Diversification ◽

Local Environments ◽

Fluctuating Environments ◽

Circadian Behavior

The plant circadian system is based on self-sustained cellular oscillations and is utilized to adapt to daily and seasonal environmental changes. The cellular circadian clocks in the above- and belowground plant organs are subjected to diverse local environments. Individual cellular clocks are affected by other cells/tissues in plants, and the intrinsic properties of cellular clocks remain to be elucidated. In this study, we showed the circadian properties of leaf- and root-derived cells of a CCA1::LUC Arabidopsis transgenic plant and demonstrated that the cells in total isolation from other cells harbor a genuine circadian clock. Quantitative and statistical analyses for individual cellular bioluminescence rhythms revealed a difference in amplitude and precision of light/dark entrainment between the two cell-types, suggesting that leaf-derived cells have a clock with a stronger persistence against fluctuating environments. Circadian systems in the leaves and roots are diversified to adapt to their local environments at the cellular level.

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The neural circadian system of mammals

Essays in Biochemistry ◽

10.1042/bse0490001 ◽

2011 ◽

Vol 49 ◽

pp. 1-17 ◽

Cited By ~ 11

Author(s):

Hugh D. Piggins ◽

Clare Guilding

Keyword(s):

Circadian Rhythms ◽

Circadian System ◽

Daily Activities ◽

Suprachiasmatic Nuclei ◽

Dark Cycle ◽

Environmental Light ◽

Endogenous Clock ◽

Central Clock

Humans and other mammals exhibit a remarkable array of cyclical changes in physiology and behaviour. These are often synchronized to the changing environmental light–dark cycle and persist in constant conditions. Such circadian rhythms are controlled by an endogenous clock, located in the suprachiasmatic nuclei of the hypothalamus. This structure and its cells have unique properties, and some of these are reviewed to highlight how this central clock controls and sculpts our daily activities.

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Anatase TiO2 Nanoparticles Induce Autophagy and Chloroplast Degradation in Thale Cress (Arabidopsis thaliana)

Environmental Science & Technology ◽

10.1021/acs.est.9b01648 ◽

2019 ◽

Vol 53 (16) ◽

pp. 9522-9532 ◽

Cited By ~ 3

Author(s):

Timothy E. Shull ◽

Jasmina Kurepa ◽

Jan A. Smalle

Keyword(s):

Arabidopsis Thaliana ◽

Tio2 Nanoparticles ◽

Anatase Tio2 ◽

Thale Cress

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Influence of D.C. electric field on growth of arabidopsis thaliana (thale-cress)

2010 Annual Report Conference on Electrical Insulation and Dielectic Phenomena ◽

10.1109/ceidp.2010.5724001 ◽

2010 ◽

Cited By ~ 4

Author(s):

T Okumura ◽

Y Muramoto ◽

N Shimizu

Keyword(s):

Arabidopsis Thaliana ◽

Electric Field ◽

Thale Cress

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A circadian oscillator in the fungus Botrytis cinerea regulates virulence when infecting Arabidopsis thaliana

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1508432112 ◽

2015 ◽

Vol 112 (28) ◽

pp. 8744-8749 ◽

Cited By ~ 67

Author(s):

Montserrat A. Hevia ◽

Paulo Canessa ◽

Hanna Müller-Esparza ◽

Luis F. Larrondo

Keyword(s):

Arabidopsis Thaliana ◽

Botrytis Cinerea ◽

Plant Pathogen ◽

Defense Mechanisms ◽

Pathogenic Fungi ◽

Circadian System ◽

Main Role ◽

Fungal Virulence ◽

Virulence Potential ◽

Plant Pathogen Interactions

The circadian clock of the plant model Arabidopsis thaliana modulates defense mechanisms impacting plant–pathogen interactions. Nevertheless, the effect of clock regulation on pathogenic traits has not been explored in detail. Moreover, molecular description of clocks in pathogenic fungi—or fungi in general other than the model ascomycete Neurospora crassa—has been neglected, leaving this type of question largely unaddressed. We sought to characterize, therefore, the circadian system of the plant pathogen Botrytis cinerea to assess if such oscillatory machinery can modulate its virulence potential. Herein, we show the existence of a functional clock in B. cinerea, which shares similar components and circuitry with the Neurospora circadian system, although we found that its core negative clock element FREQUENCY (BcFRQ1) serves additional roles, suggesting extracircadian functions for this protein. We observe that the lesions produced by this necrotrophic fungus on Arabidopsis leaves are smaller when the interaction between these two organisms occurs at dawn. Remarkably, this effect does not depend solely on the plant clock, but instead largely relies on the pathogen circadian system. Genetic disruption of the B. cinerea oscillator by mutation, overexpression of BcFRQ1, or by suppression of its rhythmicity by constant light, abrogates circadian regulation of fungal virulence. By conducting experiments with out-of-phase light:dark cycles, we confirm that indeed, it is the fungal clock that plays the main role in defining the outcome of the Arabidopsis–Botrytis interaction, providing to our knowledge the first evidence of a microbial clock modulating pathogenic traits at specific times of the day.

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