Genome-wide and heterocyst-specific circadian gene expression in the filamentous cyanobacterium Anabaena sp. strain PCC 7120

Hiroko Kushige, Hideyuki Kugenuma, Masaki Matsuoka, Shigeki Ehira, Masayuki Ohmori, Hideo Iwasaki*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

13 Citations (Scopus)


The filamentous, heterocystous cyanobacterium Anabaena sp. strain PCC 7120 is one of the simplest multicellular organisms that show both morphological pattern formation with cell differentiation (heterocyst formation) and circadian rhythms. Therefore, it potentially provides an excellent model in which to analyze the relationship between circadian functions and multicellularity. However, detailed cyanobacterial circadian regulation has been intensively analyzed only in the unicellular species Synechococcus elongatus. In contrast to the highest-amplitude cycle in Synechococcus, we found that none of the kai genes in Anabaena showed high-amplitude expression rhythms. Nevertheless,~80 clock-controlled genes were identified. We constructed luciferase reporter strains to monitor the expression of some high-amplitude genes. The bioluminescence rhythms satisfied the three criteria for circadian oscillations and were nullified by genetic disruption of the kai gene cluster. In heterocysts, in which photosystem II is turned off, the metabolic and redox states are different from those in vegetative cells, although these conditions are thought to be important for circadian entrainment and timekeeping processes. Here, we demonstrate that circadian regulation is active in heterocysts, as shown by the finding that heterocyst-specific genes, such as all1427 and hesAB, are expressed in a robust circadian fashion exclusively without combined nitrogen.

Original languageEnglish
Pages (from-to)1276-1284
Number of pages9
JournalJournal of Bacteriology
Issue number6
Publication statusPublished - 2013 Mar

ASJC Scopus subject areas

  • Microbiology
  • Molecular Biology


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