Global Mapping at the Core of the Arabidopsis Circadian Clock Defines the Network Structure of the Oscillator
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ABSTRACT:
ORGANISM(S): Arabidopsis thaliana
PROVIDER: GSE35952 | GEO | 2012/03/08
SECONDARY ACCESSION(S): PRJNA151987
REPOSITORIES: GEO
Similar Datasets
Project description:In many organisms, the circadian clock is composed of functionally coupled morning and evening oscillators that regulate the bouts of dawn and dusk activity. In Arabidopsis, oscillator coupling relies on a core loop in which the evening oscillator component TOC1 was proposed to activate a subset of morning-expressed oscillator genes. Our systems-biological approach overturns the current view of the Arabidopsis circadian clock showing that TOC1 does not function as an activator but as a timely-controlled general repressor of morning and evening oscillator components. Repression occurs through rhythmic binding to the promoters of all oscillator genes, suggesting a previously unexpected direct connection between the morning and evening loops. Examination of TOC1 genome-wide binding using TOC1 Minigene (TMG) seedlings expressing the genomic fragment of TOC1 fused to the Yellow Fluorescent Protein in a toc1-2 mutant background (TMG-YFP/toc1-2 seedlings) grown under LD cycles (12h light:12h dark).
2012-03-08 | E-GEOD-35952 | biostudies-arrayexpress
Project description:This a model from the article:
Experimental validation of a predicted feedback loop in the multi-oscillator clock of Arabidopsis thaliana.
Locke JC, Kozma-Bognár L, Gould PD, Fehér B, Kevei E, Nagy F, Turner MS, Hall A, Millar AJ
Mol. Syst. Biol.2006;Volume:2;Page:59
17102804,
Abstract:
Our computational model of the circadian clock comprised the feedback loop between LATE ELONGATED HYPOCOTYL (LHY), CIRCADIAN CLOCK ASSOCIATED 1 (CCA1) and TIMING OF CAB EXPRESSION 1 (TOC1), and a predicted, interlocking feedback loop involving TOC1 and a hypothetical component Y. Experiments based on model predictions suggested GIGANTEA (GI) as a candidate for Y. We now extend the model to include a recently demonstrated feedback loop between the TOC1 homologues PSEUDO-RESPONSE REGULATOR 7 (PRR7), PRR9 and LHY and CCA1. This three-loop network explains the rhythmic phenotype of toc1 mutant alleles. Model predictions fit closely to new data on the gi;lhy;cca1 mutant, which confirm that GI is a major contributor to Y function. Analysis of the three-loop network suggests that the plant clock consists of morning and evening oscillators, coupled intracellularly, which may be analogous to coupled, morning and evening clock cells in Drosophila and the mouse.
The model describes a three loops model of the Arabidopsis circadian clock. It provides initial conditions, parameter values and reactions for the production rates of the following species: LHY mRNA (cLm), cytoplasmic LHY (cLc), nuclear LHY (cLn), TOC1 mRNA (cTm), cytoplasmic TOC1 (cTc), nuclear TOC1 (cTn), X mRNA (cXm), cytoplasmic X (cXc), nuclear X (cXn), Y mRNA (cYm), cytoplasmic Y (cYc), nuclear Y (cYn), nuclear P (cPn), APRR7/9 mRNA, cytoplasmic APRR7/9, and nuclear APRR7/9.
The paper describes the behaviour of the model in constant light (LL) and day-night cycle (LD). However, the current model only contains the LL cycle. Some parameter values should be changed from the wild-type (WT) ones in order to simulate the effect of mutations. These changes are listed in the notes of relevant parameters.
This model originates from BioModels Database: A Database of Annotated Published Models. It is copyright (c) 2005-2009 The BioModels Team.For more information see the terms of use.To cite BioModels Database, please use Le Novère N., Bornstein B., Broicher A., Courtot M., Donizelli M., Dharuri H., Li L., Sauro H., Schilstra M., Shapiro B., Snoep J.L., Hucka M. (2006) BioModels Database: A Free, Centralized Database of Curated, Published, Quantitative Kinetic Models of Biochemical and Cellular Systems Nucleic Acids Res., 34: D689-D691.
2007-02-20 | BIOMD0000000089 | BioModels
Project description:The plant circadian clock exerts a critical role in the regulation of multiple biological processes including responses to biotic and abiotic stresses. It is estimated that the clock regulates up to 80% of the transcriptome in Arabidopsis, thus understanding the molecular mechanisms that control this rhythmic transcriptome requires identification of the targets of each clock component. The Arabidopsis core clock is partially comprised of a transcriptional regulatory loop between the MYB domain containing transcription factors CIRCADIAN CLOCK ASSOCIATED1 (CCA1) and LATE ELONGATED HYPOCOTYL (LHY), and TIMING OF CAB EXPRESSION1 (TOC1). As a key component of the clock, CCA1 is able to initiate and set the phase of clock-controlled rhythms. CCA1 regulates the transcription of several genes by directly binding to the evening element (EE) motif primarily found in the promoters of evening expressed genes. Using a genome-wide approach we have identified direct targets of CCA1 in plants grown in constant (LL) and driven conditions (LD). These CCA1 targets are enriched for a myriad of biological processes and stress responses. While many of these target genes are evening phased and contain the EE in their promoter regions, a significant subset is morning phased and lack an EE. Furthermore, several CCA1 targets do not cycle in either LL or LD or both. Expression analysis in CCA1 overexpressing plants confirms CCA1 regulation of analyzed targets. Our results emphasize an expanded role for the circadian clock in regulation of key pathways in Arabidopsis, and provide a comprehensive and solid resource for future functional studies. ChIP-Seq of CCA1-GFP plants under control of the CCA1 promoter in continuous light and diel conditions
2015-07-26 | E-GEOD-70533 | biostudies-arrayexpress
Project description:This model is from the article:
The clock gene circuit in Arabidopsis includes a repressilator with additional feedback loops
Pokhilko A, Fernández AP, Edwards KD, Southern MM, Halliday KJ, Millar AJ.
Mol Syst Biol.2012 Mar 6;8:574.
22395476,
Abstract:
Circadian clocks synchronise biological processes with the day/night cycle, using molecular mechanisms that include interlocked, transcriptional feedback loops. Recent experiments identified the evening complex (EC) as a repressor that can be essential for gene expression rhythms in plants. Integrating the EC components in this role significantly alters our mechanistic, mathematical model of the clock gene circuit. Negative autoregulation of the EC genes constitutes the clock's evening loop, replacing the hypothetical component Y. The EC explains our earlier conjecture that the morning gene PSEUDO-RESPONSE REGULATOR 9 was repressed by an evening gene, previously identified with TIMING OF CAB EXPRESSION1 (TOC1). Our computational analysis suggests that TOC1 is a repressor of the morning genes LATE ELONGATED HYPOCOTYL and CIRCADIAN CLOCK ASSOCIATED1 rather than an activator as first conceived. This removes the necessity for the unknown component X (or TOC1mod) from previous clock models. As well as matching timeseries and phase-response data, the model provides a new conceptual framework for the plant clock that includes a three-component repressilator circuit in its complex structure.
2011-08-18 | BIOMD0000000412 | BioModels
Project description:The plant circadian clock exerts a critical role in the regulation of multiple biological processes including responses to biotic and abiotic stresses. It is estimated that the clock regulates up to 80% of the transcriptome in Arabidopsis, thus understanding the molecular mechanisms that control this rhythmic transcriptome requires identification of the targets of each clock component. The Arabidopsis core clock is partially comprised of a transcriptional regulatory loop between the MYB domain containing transcription factors CIRCADIAN CLOCK ASSOCIATED1 (CCA1) and LATE ELONGATED HYPOCOTYL (LHY), and TIMING OF CAB EXPRESSION1 (TOC1). As a key component of the clock, CCA1 is able to initiate and set the phase of clock-controlled rhythms. CCA1 regulates the transcription of several genes by directly binding to the evening element (EE) motif primarily found in the promoters of evening expressed genes. Using a genome-wide approach we have identified direct targets of CCA1 in plants grown in constant (LL) and driven conditions (LD). These CCA1 targets are enriched for a myriad of biological processes and stress responses. While many of these target genes are evening phased and contain the EE in their promoter regions, a significant subset is morning phased and lack an EE. Furthermore, several CCA1 targets do not cycle in either LL or LD or both. Expression analysis in CCA1 overexpressing plants confirms CCA1 regulation of analyzed targets. Our results emphasize an expanded role for the circadian clock in regulation of key pathways in Arabidopsis, and provide a comprehensive and solid resource for future functional studies.
2015-07-26 | GSE70533 | GEO
Project description:Intercellular coupling is crucial to prevent desynchronization of cell-autonomous oscillator networks and thus, the disruption of circadian tissue functions. While, neuronal oscillators within the mammalian central clock, the suprachiasmatic nucleus (SCN), couple intercellularly via the exchange of secreted neurotransmitters, intercellular coupling among peripheral oscillators is highly debated and molecular mechanisms are unknown. In our study, we show that peripheral circadian oscillators couple intercellularly via the exchange of secreted signaling molecules and identify TGF-beta as peripheral coupling factor. TGF-beta signaling induces the cAMP response element dependent, immediate-early expression of the clock gene PER2, thereby phase-adjusting the molecular circadian oscillator. Genetic or pharmacologic disruption of TGF-beta signaling causes desynchronization of cellular oscillators resulting in amplitude reduction and increased sensitivity towards Zeitgeber cues. Our findings reveal a previously unknown mechanism of peripheral coupling and open a new perspective on the importance of peripheral clock synchrony for rhythmic organ functions and circadian health.
2021-07-23 | GSE158577 | GEO
Project description:To gain insights into the mechanisms of TOC1 function in the Arabidopsis circadian clock we performed transcriptional profiling of Wild-Type (WT) and and TOC1 overexpressor plants (TOC1-ox).
2009-09-09 | GSE18007 | GEO
Project description:Cyanobacteria are increasingly being considered for use in large-scale outdoor production of fuels and industrial chemicals. Cyanobacteria can anticipate daily changes in light availability using an internal circadian clock and rapidly alter their metabolic processes in response to changes light availability. Understanding how signals from the internal circadian clock and external light availability are integrated to control metabolic shifts will be important for engineering cyanobacteria for production in natural outdoor environments. This study has assessed how “knowing” the correct time of day, via the circadian clock, affects metabolic changes when a cyanobacterium goes through a dark-to-light transition. Our data show that the circadian clock plays an important role in inhibiting activation of the oxidative pentose phosphate pathway in the morning. Synechococcus elongatus PCC 7942 is a genetically tractable model cyanobacterium that has been engineered to produce industrially relevant biomolecules and is the best-studied model for a prokaryotic circadian clock. However, the organism is commonly grown in continuous light in the laboratory, and data on metabolic processes under diurnal conditions are lacking. Moreover, the influence of the circadian clock on diurnal metabolism has been investigated only briefly. Here, we demonstrate that the circadian oscillator influences rhythms of metabolism during diurnal growth, even though light–dark cycles can drive metabolic rhythms independently. Moreover, the phenotype associated with loss of the core oscillator protein, KaiC, is distinct from that caused by absence of the circadian output transcriptional regulator, RpaA (regulator of phycobilisome-associated A). Although RpaA activity is important for carbon degradation at night, KaiC is dispensable for those processes. Untargeted metabolomics analysis and glycogen kinetics suggest that functional KaiC is important for metabolite partitioning in the morning. Additionally, output from the oscillator functions to inhibit RpaA activity in the morning, and kaiC-null strains expressing a mutant KaiC phosphomimetic, KaiC-pST, in which the oscillator is locked in the most active output state, phenocopies a ΔrpaA strain. Inhibition of RpaA by the oscillator in the morning suppresses metabolic processes that normally are active at night, and kaiC-null strains show indications of oxidative pentose phosphate pathway activation as well as increased abundance of primary metabolites. Inhibitory clock output may serve to allow secondary metabolite biosynthesis in the morning, and some metabolites resulting from these processes may feed back to reinforce clock timing.
2016-04-28 | ST000395 | MetabolomicsWorkbench
Project description:Cyanobacteria are increasingly being considered for use in large-scale outdoor production of fuels and industrial chemicals. Cyanobacteria can anticipate daily changes in light availability using an internal circadian clock and rapidly alter their metabolic processes in response to changes light availability. Understanding how signals from the internal circadian clock and external light availability are integrated to control metabolic shifts will be important for engineering cyanobacteria for production in natural outdoor environments. This study has assessed how “knowing” the correct time of day, via the circadian clock, affects metabolic changes when a cyanobacterium goes through a dark-to-light transition. Our data show that the circadian clock plays an important role in inhibiting activation of the oxidative pentose phosphate pathway in the morning. Synechococcus elongatus PCC 7942 is a genetically tractable model cyanobacterium that has been engineered to produce industrially relevant biomolecules and is the best-studied model for a prokaryotic circadian clock. However, the organism is commonly grown in continuous light in the laboratory, and data on metabolic processes under diurnal conditions are lacking. Moreover, the influence of the circadian clock on diurnal metabolism has been investigated only briefly. Here, we demonstrate that the circadian oscillator influences rhythms of metabolism during diurnal growth, even though light–dark cycles can drive metabolic rhythms independently. Moreover, the phenotype associated with loss of the core oscillator protein, KaiC, is distinct from that caused by absence of the circadian output transcriptional regulator, RpaA (regulator of phycobilisome-associated A). Although RpaA activity is important for carbon degradation at night, KaiC is dispensable for those processes. Untargeted metabolomics analysis and glycogen kinetics suggest that functional KaiC is important for metabolite partitioning in the morning. Additionally, output from the oscillator functions to inhibit RpaA activity in the morning, and kaiC-null strains expressing a mutant KaiC phosphomimetic, KaiC-pST, in which the oscillator is locked in the most active output state, phenocopies a ΔrpaA strain. Inhibition of RpaA by the oscillator in the morning suppresses metabolic processes that normally are active at night, and kaiC-null strains show indications of oxidative pentose phosphate pathway activation as well as increased abundance of primary metabolites. Inhibitory clock output may serve to allow secondary metabolite biosynthesis in the morning, and some metabolites resulting from these processes may feed back to reinforce clock timing.
2016-05-04 | ST000394 | MetabolomicsWorkbench
Project description:In mammalian tissues circadian gene expression can be driven by local oscillators or systemic signals controlled by the master pacemaker in the suprachiasmatic nucleus. Here we show that simulated body temperature cycles, but not peripheral oscillators, can control the rhythmic expression of Cold-Inducible RNA binding Protein (CIRP) in cultured fibroblasts. In turn, loss-of-function experiments indicate that CIRP is required for high amplitude circadian gene expression. The transcriptome-wide identification of CIRP-bound RNAs by a biotin-streptavidin based CLIP-seq procedure revealed several CIRP-bound transcripts encoding circadian oscillator proteins. One of these, CLOCK, accumulated to particularly low levels in CIRP-depleted fibroblasts. Since ectopic expression of CLOCK improved circadian gene expression in these cells, we surmise that CIRP confers robustness to circadian oscillators via the regulation of CLOCK expression.
2012-08-24 | GSE37685 | GEO