Circadian rhythms persist without transcription in a eukaryote

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Circadian rhythms are ubiquitous in eukaryotes, and coordinate numerous aspects of behaviour, physiology and metabolism, from sleep/wake cycles in mammals to growth and photosynthesis in plants. This daily timekeeping is thought to be driven by transcriptionaltranslational feedback loops, whereby rhythmic expression of clock- gene products regulates the expression of associated genes in approximately 24-hour cycles. The specific transcriptional components differ between phylogenetic kingdoms. The unicellular pico-eukaryotic alga Ostreococcus tauri possesses a naturally minimized clock, which includes many features that are shared with plants, such as a central negative feedback loop that involves the morning-expressed CCA1 and evening-expressed TOC1 genes. Given that recent observations in animals and plants have revealed prominent post-translational contributions to timekeeping, a reappraisal of the transcriptional contribution to oscillator function is overdue. Here we show that non-transcriptional mechanisms are sufficient to sustain circadian timekeeping in the eukaryotic lineage, although they normally function in conjunction with transcriptional components. We identify oxidation of peroxiredoxin proteins as a transcription-independent rhythmic biomarker, which is also rhythmic in mammals. Moreover we show that pharmacological modulators of the mammalian clock mechanism have the same effects on rhythms in Ostreococcus. Post-translational mechanisms, and at least one rhythmic marker, seem to be better conserved than transcriptional clock regulators. It is plausible that the oldest oscillator components are non-transcriptional in nature, as in cyanobacteria, and are conserved across kingdoms.


  • John S. O'Neill
  • Gerben Van Ooijen
  • Laura E. Dixon
  • Carl Troein
  • Florence Corellou
  • François-Yves Bouget
  • Akhilesh B. Reddy
  • Andrew J. Millar
Externa organisationer
  • Centre for Systems Biology at Edinburgh
  • University of Cambridge
  • University of Edinburgh
  • UPMCUniv Paris 06
  • Laboratoire d'Océanographie Microbienne (LOMIC)
  • Versailles Saint-Quentin-en-Yvelines University

Ämnesklassifikation (UKÄ) – OBLIGATORISK

  • Genetik
  • Växtbioteknologi
Sidor (från-till)554-558
Antal sidor5
StatusPublished - 2011 jan 27
Peer review utfördJa
Externt publiceradJa