Gene expression timecourse in clock rescue strains
Ontology highlight
ABSTRACT:
ORGANISM(S): Synechococcus elongatus PCC 7942 = FACHB-805
PROVIDER: GSE50920 | GEO | 2013/12/04
SECONDARY ACCESSION(S): PRJNA219376
REPOSITORIES: GEO
Similar Datasets
Project description:The goal of this experiment was to determine whether global circadian gene expression oscillation depends strictly on the presence of rpaA, even when the KaiABC post-translational oscillator is oscillating with a circadian period. Strains deleted for rpaA lack functional KaiABC post-translational oscillators because their reduced kaiBC expression level leads to a non-permissive Kai protein stoichiometry. We restored KaiABC post-translational oscillator function in a M-NM-^TrpaA M-NM-^TkaiBC strain by ectopic expression of kaiBC from the Ptrc promoter and used microarrays to measure the timecourse of gene expression globally. As a control, we used microarrays to measure the gene expression timecourse in a M-NM-^TkaiBC Ptrc::kaiBC strain, in which gene expression was expected to be rhythmic (Y Murayama et al, J. Bac. 198, 2008), as it is in the pure wild-type strain. Cultures were grown in a flasks bubbled with 1% CO2 in air, initially in the absence of IPTG. Cultures were treated with two consecutive light/dark cycles and released into continuous light at time T = 0, at which time IPTG was added to a final concentration of 6 M-BM-5M. Cultures were samples every 4 hours for 44 h between T = 24 h and T = 68 h, inclusive. Gene expression at each timepoint was compared to the time-averaged gene expression (determined using a pool of equal mass quantities of RNA from all timepoints) using a two-color Agilent microarray.
2013-12-04 | E-GEOD-50920 | biostudies-arrayexpress
Project description:In the unicellular cyanobacterium, Synechococcus elongatus PCC 7942, essentially all promoter activities are under the control of the circadian clock in continuous light (LL) conditions. Here, we employed high-density oligonucleotide arrays to explore comprehensive profiles of genome-wide Synechococcus gene expression in wild type, kaiABC-null and kaiC-overexpressor strains under LL and continuous dark (DD) conditions. In the wild type strain more than 30% of transcripts significantly oscillated in a circadian fashion, peaking at subjective dawn and dusk. Such circadian control was nullified in kaiABC-null strains. Although KaiC has been proposed to globally repress gene expression, our analysis revealed that dawn expressing genes were upregulated by kaiC-overexpression, such that the clock was arrested at subjective dawn. Transfer of cells to continuous dark (DD) conditions from LL immediately suppressed expression of most of genes, while the clock keeps time even in the absence of transcriptional feedback. Thus, the Synechococcus genome seems primarily regulated by the light/dark cycles and dramatically modified by the protein-based circadian oscillator. Keywords: timecourse data (~48 hours under continuous light or darkness) from Synechococcus elongatus PCC 7942 (wild type, kaiABC-null, and inducible kaiC-overexpressor) strains
2009-08-01 | GSE14225 | GEO
Project description:The cyanobacterium Synechococcus elongatus contains a circadian clock which coordinates circadian changes in gene expression of a large percentage of its genes. The response regulator RpaA has been implicated as an important regulator of many circadian genes, but the role of this protein in regulating changes in gene expression genome-wide is not known. We show that deletion of rpaA abrogates circadian gene expression genome-wide and arrests cells in a gene expression state highly similar to that of wildtype cells in the morning. Furthermore, we show that RpaA binds DNA in an circadian manner that is dependent on phosphorylation of the protein. To demonstrate the sufficiency of phosphorylated RpaA in driving global changes in gene expression, we used RNA sequencing to measure changes in gene expression elicited by a phosphomimetic of RpaA (RpaA D53E) and compared these changes to those that occur during a circadian cycle in wildtype cells. This analysis reveals that induction of RpaA D53E is sufficient to drive all circadian gene expression changes that happen from dawn to dusk in wildtype cells. Interestingly, the dynamics of gene expression elicited by RpaA D53E induction mirror those observed during a circadian cycle in wildtype cells, suggesting that the dynamics of circadian gene expression and hard-wired in the regulon downstream of RpaA. Enriched mRNA was prepared from synchronized wildtype S. elongatus cells every four hours over a circadian cycle and sequenced using the Illumina TruSeq Stranded mRNA Sample Prep Kit and Illumina HiSeq technology. To test the role of phosphorylated RpaA in driving circadian gene expression, we generated a strain which we refer to as OX-D53E that lacks core clock components (M-NM-^TrpaA, M-NM-^TkaiBC) with an RpaA phosphomimetic (RpaA D53E) under the control of an IPTG-inducible promoter (Ptrc::rpaAD53E). We used the same methodology to measure gene expression in OX-D53E before and after induction of RpaA D53E. As a control, we also measured gene expression in the OX-D53E strain over time in the absence of IPTG. Also, we generated a strain similar to OX-D53E in which the only difference was that no gene was inserted downstream of the IPTG inducible promoter (OX-Empty). We measured gene expressio in OX-Empty before and after IPTG addition to test for off-target effects of IPTG.
2013-12-04 | E-GEOD-51112 | biostudies-arrayexpress
Project description:The response regulator RpaA is required for control of genome-wide gene expression by the cyanobacterial circadian clock. RpaA is predicted to be a DNA binding protein based on sequence homology, but prior studies have been unable to detect binding in vitro or in vivo to a small panel of promoters. We used ChIP-Seq to determine whether RpaA associates with DNA in vivo, and if so, with what dynamics. We find that RpaA binds to over 100 location in the genome in a circadian manner, with strongest binding occuring around subjective dusk. Analysis of these binding sites shows that RpaA directly regulates the expression of clock components to generate feedback on the core oscillator, and also regulates expression of a small set of circadian effectors that in turn orchestrate global expression rhythms.
2013-12-04 | GSE51093 | GEO
Project description:In the unicellular cyanobacterium, Synechococcus elongatus PCC 7942, essentially all promoter activities are under the control of the circadian clock in continuous light (LL) conditions. Here, we employed high-density oligonucleotide arrays to explore comprehensive profiles of genome-wide Synechococcus gene expression in wild type, kaiABC-null and kaiC-overexpressor strains under LL and continuous dark (DD) conditions. In the wild type strain more than 30% of transcripts significantly oscillated in a circadian fashion, peaking at subjective dawn and dusk. Such circadian control was nullified in kaiABC-null strains. Although KaiC has been proposed to globally repress gene expression, our analysis revealed that dawn expressing genes were upregulated by kaiC-overexpression, such that the clock was arrested at subjective dawn. Transfer of cells to continuous dark (DD) conditions from LL immediately suppressed expression of most of genes, while the clock keeps time even in the absence of transcriptional feedback. Thus, the Synechococcus genome seems primarily regulated by the light/dark cycles and dramatically modified by the protein-based circadian oscillator. Keywords: timecourse data (~48 hours under continuous light or darkness) from Synechococcus elongatus PCC 7942 (wild type, kaiABC-null, and inducible kaiC-overexpressor) strains Wild type (WT), kaiABC-null (Dkai), and inducible kaiC-overexpressor (oxC) S. elongatus PCC 7942 strains were analyzed under continuous light (LL), continuous dark (DD) using Affymetrix high-density oligonucleotide microarrays (GeneChip CustomExpress Arrays) representing predicted 2,515 protein-coding genes on the genome of Synechococcus elongatus PCC 6301, which can be used also to the almost homologous strain, S. elongatus PCC 7942: Two independent experiments in WT under LL (hours 0 to 52) and DD (hours 0 to 48); Two independent experiments in Dkai under LL (hours 0 to 48); Two independent experiments in oxC under LL in the presence or absence of an inducer, IPTG, from hour 25 to 33 in LL; a single experiment in WT under DD in the presence of an transcriptional inhibitor, rifampicin.
2009-07-31 | E-GEOD-14225 | biostudies-arrayexpress
Project description:The cyanobacterium Synechococcus elongatus contains a circadian clock which coordinates circadian changes in gene expression of a large percentage of its genes. The response regulator RpaA has been implicated as an important regulator of many circadian genes, but the role of this protein in regulating changes in gene expression genome-wide is not known. We show that deletion of rpaA abrogates circadian gene expression genome-wide and arrests cells in a gene expression state highly similar to that of wildtype cells in the morning. Furthermore, we show that RpaA binds DNA in an circadian manner that is dependent on phosphorylation of the protein. To demonstrate the sufficiency of phosphorylated RpaA in driving global changes in gene expression, we used RNA sequencing to measure changes in gene expression elicited by a phosphomimetic of RpaA (RpaA D53E) and compared these changes to those that occur during a circadian cycle in wildtype cells. This analysis reveals that induction of RpaA D53E is sufficient to drive all circadian gene expression changes that happen from dawn to dusk in wildtype cells. Interestingly, the dynamics of gene expression elicited by RpaA D53E induction mirror those observed during a circadian cycle in wildtype cells, suggesting that the dynamics of circadian gene expression and hard-wired in the regulon downstream of RpaA.
2013-12-04 | GSE51112 | GEO
Project description:The response regulator RpaA is required for control of genome-wide gene expression by the cyanobacterial circadian clock. RpaA is predicted to be a DNA binding protein based on sequence homology, but prior studies have been unable to detect binding in vitro or in vivo to a small panel of promoters. We used ChIP-Seq to determine whether RpaA associates with DNA in vivo, and if so, with what dynamics. We find that RpaA binds to over 100 location in the genome in a circadian manner, with strongest binding occuring around subjective dusk. Analysis of these binding sites shows that RpaA directly regulates the expression of clock components to generate feedback on the core oscillator, and also regulates expression of a small set of circadian effectors that in turn orchestrate global expression rhythms. Crosslinked samples were acquired every four hours from a turbidostatic wild-type (AMC408) cultures in constant light (LL) following entrainment with two light-dark (LD) cycles. As a negative control, we acquired samples similarly from an M-NM-^TrpaA culture. Chromatin immunoprecipitation was performed on each sample from wht wild-type and from a pool of all samples from the M-NM-^TrpaA culture. Libraries were prepared from the ChIP samples and sequenced with Illumina technology. For the wild-type, biological replicate samples were acquired at times of maximum and minimum RpaA binding.
2013-12-04 | E-GEOD-51093 | biostudies-arrayexpress
Project description:Like many other organisms, cyanobacteria exhibit rhythmic gene expression with a period length of 24 hours to adapt to daily environmental changes. In the model organism Synechococcus elongatus PCC 7942 the central oscillator consists of three proteins: KaiA, KaiB and KaiC and utilizes the histidine kinase SasA and its response regulator RpaA as output-signaling pathway. Synechocystis sp. PCC 6803 contains two additional homologs of the kaiB and kaiC genes. Here we demonstrate that RpaA interacts with the core oscillator KaiAB1C1 of Synechocystis sp. PCC 6803 via SasA, similar to Synechococcus elongatus PCC 7942. However, interaction with the additional Kai homologs was not detected, suggesting different signal transduction components for the clock homologs. Inactivation of rpaA in Synechocystis sp. PCC 6803, lead to reduced viability of the mutant in light-dark cycles that aggravated under mixotrophic growth conditions. Chemoheterotrophic growth in the dark was abolished completely. In accordance, transcriptomic data revealed that RpaA is involved in the regulation of genes related to CO2‑acclimation and carbon metabolism under diurnal light conditions. Further, our results indicate that RpaA functions in the posttranslational regulation of glycogen metabolism as well, and a potential link between the circadian clock and motility was identified.
2018-10-01 | GSE116795 | GEO
Project description:We analyzed the gene expression changes in the wild type and the delta kaiAB1C1 mutant at six time points after a 12 hours dark incubation. RNA-Seq provides a much higher senisitivity and resolution in comparison to previously performed micro array experiments. We aim to get a better understanding how the circadian oscillator which is encoded by the kaiABC genes regulates the overall gene expression in Synechocystis sp. PCC 6803.
2022-06-06 | GSE132275 | GEO
Project description:The transcription factor RpaA is the master regulator of circadian transcription in cyanobacteria, driving genome-wide oscillations in mRNA abundance. Deletion of rpaA has no effect on viability in constant light conditions, but renders cells inviable in cycling conditions when light and dark periods alternate. We investigated the mechanisms underlying this viability defect. We performed RNA-seq experiment using the rpaA- “clock rescue” and “clock rescue” strains and we show that the rpaA- “clock rescue” strain is defective in transcription of genes crucial for utilization of carbohydrate stores at night.
2017-02-15 | GSE89999 | GEO