Open Access Research article

Orchestrated transcription of biological processes in the marine picoeukaryote Ostreococcus exposed to light/dark cycles

Annabelle Monnier14, Silvia Liverani2, Régis Bouvet1, Béline Jesson1, Jim Q Smith2, Jean Mosser134, Florence Corellou56 and François-Yves Bouget56*

Author Affiliations

1 OUEST-genopole(R)transcriptome platform, IFR 140 GFAS, Faculté de Médecine, 2 avenue du Pr Léon Bernard, CS 34317 35043 Rennes Cedex, France

2 Department of Statistics, University of Warwick, Coventry CV4 7AL, UK

3 Medical Genomics Unit, Molecular Genetics and Biochemistry Department, Hospital Center, Rennes, France

4 CNRS UMR 6061 "Génétique et Développement", Régulation transcriptionnelle et Oncogenèse, Université de Rennes 1, IFR140 GFAS, Faculté de médecine, 2 avenue du Pr Léon Bernard, CS 34317, 35043 Rennes Cedex, France

5 UPMC University Paris 06, UMR7621 Laboratoire d'Océanographie Microbienne, Observatoire Océanologique, F-66651, Banyuls/mer, France

6 CNRS, UMR7621 Laboratoire d'Océanographie Microbienne, Observatoire Océanologique, F-66651, Banyuls/mer, France

For all author emails, please log on.

BMC Genomics 2010, 11:192  doi:10.1186/1471-2164-11-192

Published: 22 March 2010



Picoeukaryotes represent an important, yet poorly characterized component of marine phytoplankton. The recent genome availability for two species of Ostreococcus and Micromonas has led to the emergence of picophytoplankton comparative genomics. Sequencing has revealed many unexpected features about genome structure and led to several hypotheses on Ostreococcus biology and physiology. Despite the accumulation of genomic data, little is known about gene expression in eukaryotic picophytoplankton.


We have conducted a genome-wide analysis of gene expression in Ostreococcus tauri cells exposed to light/dark cycles (L/D). A Bayesian Fourier Clustering method was implemented to cluster rhythmic genes according to their expression waveform. In a single L/D condition nearly all expressed genes displayed rhythmic patterns of expression. Clusters of genes were associated with the main biological processes such as transcription in the nucleus and the organelles, photosynthesis, DNA replication and mitosis.


Light/Dark time-dependent transcription of the genes involved in the main steps leading to protein synthesis (transcription basic machinery, ribosome biogenesis, translation and aminoacid synthesis) was observed, to an unprecedented extent in eukaryotes, suggesting a major input of transcriptional regulations in Ostreococcus. We propose that the diurnal co-regulation of genes involved in photoprotection, defence against oxidative stress and DNA repair might be an efficient mechanism, which protects cells against photo-damage thereby, contributing to the ability of O. tauri to grow under a wide range of light intensities.