Project description:We used the recently developed Excision Repair-sequencing (XR-seq) method to study genome-wide repair of UV-induced DNA damage in Arabidopsis. We found that the repair of cyclobutane pyrimidine dimers for a large fraction of the genome is controlled by the joint actions of the circadian clock and transcription by RNA polymerase II. Arabidopsis has a relatively compact genome, and a large fraction of the genes are controlled by the circadian clock. Our data on the interface of these two global regulatory systems reveal very strong repair preference of the transcribed strands of Arabidopsis genes, 10 to 30% of which are circadian time-dependent. Thus, throughout the day, Arabidopsis exhibits enormous dynamic range in repair to cope with exposure to sunlight.
Project description:Plant responses to the environment are shaped by the external stimuli and internal signaling pathways. In both the model plant Arabidopsis thaliana and crop species, circadian clock factors have been identified as critical for growth, flowering and circadian rhythms. Outside of A. thaliana, however, little is known about the molecular function of clock genes. Therefore, we sought to compare the function of Brachypodium distachyon and Seteria viridis orthologs of EARLY FLOWERING3, a key clock gene in A. thaliana. To identify both cycling genes and putative ELF3 functional orthologs in S. viridis, a circadian RNA-seq dataset and online query tool (Diel Explorer) was generated as community resource to explore expression profiles of Setaria genes under constant conditions after photo- or thermo-entrainment. The function of ELF3 orthologs from A. thaliana, B. distachyon, and S. viridis were tested for complementation of an elf3 mutation in A. thaliana. Despite comparably low sequence identity versus AtELF3 (< 37%), both monocot orthologs were capable of rescuing hypocotyl elongation, flowering time and arrhythmic clock phenotypes. Molecular analysis using affinity purification and mass spectrometry to compare physical interactions also found that BdELF3 and SvELF3 could be integrated into similar complexes and networks as AtELF3, including forming a composite evening complex. Thus, we find that, despite 180 million years of separation, BdELF3 and SvELF3 can functionally complement loss of ELF3 at the molecular and physiological level.
Project description:Broadly expressed transcriptions factors (TFs) control tissue-specific programs of gene expression through interactions with local TF networks. Prime examples are the circadian clock TFs CLOCK (CLK) and CYCLE (CYC or BMAL1): while they control a core transcriptional circuit throughout animal bodies, downstream clock target genes and circadian physiology are tissue-specific. Here, we use ChIP-seq to determine the regulatory targets of Drosophila CLK and CYC, which we epitope-tagged by homologous recombination. Both TFs have distinct binding sites in heads versus bodies, suggesting that they directly control tissue-specific downstream target genes. Analysis of these context-specific binding sites revealed distinct sequence motifs for putative clock partner factors, including a motif for the GATA factor SERPENT (SRP). SRP indeed synergistically enhances CLK/CYC-mediated activity of a cis-regulatory region bound by CLK/CYC specifically in bodies. These results reveal how universal clock circuits can generate tissue-specific outputs and demonstrate an approach to dissect regulatory interactions more generally. We sequenced ChIP and input samples, as well as M-bM-^@M-^\mockM-bM-^@M-^] samples for which we performed ChIP with the V5 antibody from wildtype w- flies (not carrying the V5 tag) for two independent biological replicates each, summing to 24 libraries in total.
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
Project description:Zhou2015 - Circadian clock with immune
regulator NPR1
Arabidopsis clock model modified from
P2012 (Pokhilko et al., 2013 -
BIOMD0000000445)
model to include the master immune regulator NPR1 coupling to LHY,
TOC1 and PRR7.
Triggers: The Global Quantities contain triggers that allow
one to change coupling settings, Salicyclic acid (SA) treatment and
npr1 mutants.
LHY_on: true->NPR1 couples to LHY
PRR7_on: true->NPR1 couples to PRR7
WT: true->WT plants, false->npr1 mutant plants
SA: true->SA treated plants, false->no treatment
This model has L=1, i.e. operates only under constant light
conditions and is not aiming to make preditions under diurnal
conditions. Due to period overshoot only time points after 28h are
relevant.
This model is described in the article:
Redox rhythm reinforces the
circadian clock to gate immune response.
Zhou M, Wang W, Karapetyan S, Mwimba
M, Marqués J, Buchler NE, Dong X.
Nature 2015 Jun;
Abstract:
Recent studies have shown that in addition to the
transcriptional circadian clock, many organisms, including
Arabidopsis, have a circadian redox rhythm driven by the
organism's metabolic activities. It has been hypothesized that
the redox rhythm is linked to the circadian clock, but the
mechanism and the biological significance of this link have
only begun to be investigated. Here we report that the master
immune regulator NPR1 (non-expressor of pathogenesis-related
gene 1) of Arabidopsis is a sensor of the plant's redox state
and regulates transcription of core circadian clock genes even
in the absence of pathogen challenge. Surprisingly, acute
perturbation in the redox status triggered by the immune signal
salicylic acid does not compromise the circadian clock but
rather leads to its reinforcement. Mathematical modelling and
subsequent experiments show that NPR1 reinforces the circadian
clock without changing the period by regulating both the
morning and the evening clock genes. This balanced network
architecture helps plants gate their immune responses towards
the morning and minimize costs on growth at night. Our study
demonstrates how a sensitive redox rhythm interacts with a
robust circadian clock to ensure proper responsiveness to
environmental stimuli without compromising fitness of the
organism.
This model is hosted on
BioModels Database
and identified by:
BIOMD0000000577.
To cite BioModels Database, please use:
BioModels Database:
An enhanced, curated and annotated resource for published
quantitative kinetic models.
To the extent possible under law, all copyright and related or
neighbouring rights to this encoded model have been dedicated to
the public domain worldwide. Please refer to
CC0
Public Domain Dedication for more information.
Project description:Background: Identifying the gene regulatory networks governing physiological signal integration remains an important challenge in circadian biology. Epidermal growth factor receptor (EGFR) has been implicated in circadian function and EGFR is expressed in the suprachiasmatic nucleus (SCN), the core circadian pacemaker. The transcription networks downstream of EGFR in the SCN are unknown, but by analogy to other SCN inputs we expect the response to EGFR activation to depend on circadian timing and thus be “circadian context–dependent”. Results: We have undertaken a systems level analysis of EGFR circadian context–dependent signaling in the SCN. We collected gene expression profiles to study how the SCN response to EGFR activation depends on circadian timing. Mixed–model analysis of variance (ANOVA) was employed to identify genes with circadian context–dependent EGFR regulation. The expression data was integrated with transcription factor (TF) binding predictions through gene group enrichment analyses to generate robust hypotheses about TFs responsible for the circadian phase–dependent EGFR responses. Conclusions: The analysis results suggest that the transcriptional response to EGFR signaling in the SCN may be partly mediated by established EGFR signaling regulated TFs (AP1, Ets1), TFs involved in circadian clock entrainment (CREB), and by core clock TFs (Rorα). qRT-PCR measurements of several TF expression levels support a model in which circadian context-dependent EGFR responses are partly achieved by circadian regulation of upstream signaling components. Our study suggests an important role for EGFR signaling in SCN function and provides an example for gaining physiological insights through systems-level analysis. Keywords: dose response; repeat sample
Project description:we determine genome-wide binding profiles of a maize CCA1 homolog, ZmCCA1b, in maize inbreds and F1 hybrids at different times of the day. ZmCCA1b is characterized as a central clock regulator gene with evolutionarily conserved molecular and circadian functions and nonadditively expressed in F1 hybrid seedlings. ZmCCA1b binds to over 4,300 target genes in the maize genomes, of which annotation confirms energy metabolic pathways as the main output. We report that an altered temporal binding activity of ZmCCA1b in the hybrid seedlings, which increases expression of carbon fixation genes, increases carbon fixation rates and biomass, demonstrating a novel example of how circadian-regulatory networks directly contribute to growth vigor in maize hybrids. These results collectively offer new insights into clock-mediated regulation of growth vigor in hybrid plants and crops. Profiling genome-wide binding events of ZmCCA1b in the maize inbreds and F1 hybrids at ZT3, ZT9 and ZT15 using chromatin immunoprecipitation followed by deep sequencing (ChIP-seq). 2 biological replicates for each sample were used. Input DNA sample corresponding to each ChIP sample was also sequenced in parallel. We have developed a native antibody for the protein (GRMZM2G014902; epitope: residues 11-77) for the ChIP-seq study.
Project description:The transition from vegetative to reproductive development is one of the most important phase changes in the plant life cycle. This step is controlled by various environmental signals that are integrated at the molecular level by so-called floral integrators. One such floral integrator in Arabidopsis (Arabidopsis thaliana) is the MADS domain transcription factor SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 (SOC1). Despite extensive genetic studies, little is known about the transcriptional control of SOC1, and we are just starting to explore the network of genes under the direct control of SOC1 transcription factor complexes. Here, we show that several MADS domain proteins, including SOC1 heterodimers, are able to bind SOC1 regulatory sequences. Genome-wide target gene analysis by ChIP-seq confirmed the binding of SOC1 to its own locus and shows that it also binds to a plethora of flowering-time regulatory and floral homeotic genes. In turn, the encoded floral homeotic MADS domain proteins appear to bind SOC1 regulatory sequences. Subsequent in planta analyses revealed SOC1 repression by several floral homeotic MADS domain proteins, and we show that, mechanistically, this depends on the presence of the SOC1 protein. Together, our data show that SOC1 constitutes a major hub in the regulatory networks underlying floral timing and flower development and that these networks are composed of many positive and negative autoregulatory and feedback loops. The latter seems to be crucial for the generation of a robust flower-inducing signal, followed shortly after by repression of the SOC1 floral integrator. A. thaliana SOC1 ChIP-seq w. control, 3 replicates