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Transcriptional profile of Synechococcus in the dark or light with or without photosynthesis inhibitors

ABSTRACT: In the unicellular cyanobacterium, Synechococcus elongatus PCC 7942, dramatically reduces the transcription rate in the dark (dark repression), and its cellular functions enormously depend on light as an energy source through photosynthetic activity. Here, we employed high-density oligonucleotide arrays to investigate comprehensive profiles of genome-wide Synechococcus gene expression when illuminated or dark-acclimated cells are treated with photosynthesis inhibitors DCMU or DBMIB. In addition, we added rifampicin to the DBMIB-treated cells in the dark, and analyzed genome-wide expression profiles. Treatment with DCMU or DBMIB under illuminated condition mimicked dark-repression-like genome-wide transcription profiles. Addition of DBMIB under dark condition largely attenuated dark-repression and kept relatively large amount of transcripts, this high-transcripts level still kept when rifampicin was additionally administered.

ORGANISM(S): Synechococcus elongatus PCC 7942 = FACHB-805 Synechococcus elongatus PCC 6301

PROVIDER: GSE55637 | GEO | 2015/06/01

SECONDARY ACCESSION(S): PRJNA240672

REPOSITORIES: GEO

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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.

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Transcriptional profile of Synechococcus in the dark or light with or without photosynthesis inhibitors

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