Damped circadian oscillation in the absence of KaiA in Synechococcus

Naohiro Kawamoto, Hiroshi Ito, Isao T. Tokuda, Hideo Iwasaki

    Research output: Contribution to journalArticlepeer-review

    19 Citations (Scopus)


    Proteins KaiA, KaiB and KaiC constitute a biochemical circadian oscillator in the cyanobacterium Synechococcus elongatus. It has been reported kaiA inactivation completely abolishes circadian oscillations. However, we show here that kaiBC promoter activity exhibits a damped, low-amplitude oscillation with a period of approximately 24 h in kaiA-inactivated strains. The damped rhythm resonates with external cycles with a period of 24–26 h, indicating that its natural frequency is similar to that of the circadian clock. Double-mutation experiments reveal that kaiC, kaiB, and sasA (encoding a KaiC-binding histidine kinase) are all required for the damped oscillation. Further analysis suggests that the kaiA-less damped transcriptional rhythm requires KaiB-KaiC complex formation and the transcription-translation feedback loop, but not the KaiC phosphorylation cycle. Our results provide insights into mechanisms that could potentially underlie the diurnal/circadian behaviors observed in other bacterial species that possess kaiB and kaiC homologues but lack a kaiA homologue.

    Original languageEnglish
    Article number2242
    JournalNature communications
    Issue number1
    Publication statusPublished - Dec 1 2020

    All Science Journal Classification (ASJC) codes

    • General Chemistry
    • General Biochemistry,Genetics and Molecular Biology
    • General Physics and Astronomy


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