Cyanobacterial daily life with Kai-based circadian and diurnal genome-wide transcriptional control in Synechococcus elongatus

Hiroshi Ito, Michinori Mutsuda, Yoriko Murayama, Jun Tomita, Norimune Hosokawa, Kazuki Terauchi, Chieko Sugita, Mamoru Sugita, Takao Kondo, Hideo Iwasaki*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

138 Citations (Scopus)


In the unicellular cyanobacterium Synechococcus elongatus PCC 7942, essentially all promoter activities are under the control of the circadian clock under continuous light (LL) conditions. Here, we used 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 strains, >30% of transcripts oscillated significantly in a circadian fashion, peaking at subjective dawn and dusk. Such circadian control was severely attenuated in kaiABC-null strains. Although it has been proposed that KaiC globally represses gene expression, our analysis revealed that dawn-expressed genes were up-regulated by kaiC-overexpression so that the clock was arrested at subjective dawn. Transfer of cells to DD conditions from LL immediately suppressed expression of most of the genes, while the clock kept even time in the absence of transcriptional feedback. Thus, the Synechococcus genome seems to be primarily regulated by light/dark cycles and is dramatically modified by the protein-based circadian oscillator.

Original languageEnglish
Pages (from-to)14168-14173
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number33
Publication statusPublished - 2009 Aug 18


  • Circadian clock
  • Cyanobacteria
  • Genome-wide expression
  • KaiC
  • Light:dark

ASJC Scopus subject areas

  • General


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