Ostreococcus tauri

Taxonomy: Eukaryota; Viridiplantae; Chlorophyta; Prasinophyceae; Mamiellales; Ostreococcus


Ostreococcus tauri is a unicellular green alga that was discovered in the Mediterranean Thau lagoon (France) in 1994. With a size less than 1 µm , comparable with the size of a bacterium, it is the smallest eukaryotic organism described until now. Its cellular organisation is rather simple with a relative large nucleus with only one nuclear pore, a single chloroplast, one mitochondrion, one Golgi body and a very reduced cytoplasmatic compartment. The presence of only one chloroplast and mitochondrium makes it interesting to use not only for evolutionary studies, but also for experimental studies. Morphologically, the absence of flagella is the most typical characteristic of Ostreococcus tauri compared with other green algae. Apart from this simple cellular structure, the genome size of Ostreococcus tauri is the smallest of all known eukaryotes. The nuclear genome is about 12 Mb, fragmented into 20 chromosomes, ranging in size from 120 to 1500 Kb. Phylogenetic analysis placed Ostreococcus tauri within the Prasinophyceae, an early branch of the Chlorophyta (green algae).

After sequencing its genome (Laboratoire Arago, Banyuls, France), the annotation will be done by members of our team. Once the annotation will be complete, a comparative analysis of Ostreococcus tauri and Chlamydomonas reinhardtii, another green algae, will be performed. This will provide us an insight in the genome organization and gene content (different gene families) among the green algae. Afterwards, other members of the green lineage (Physcomitrella patens [moss], Arabidopsis thaliana and Oryza Sativa) will be used in comparative analyses. Using these other species will give us the chance to see how plant genomes, and particular different gene families within the green lineage, have evolved during time.

In collaboration with:



Blanc-Mathieu, R., Verhelst, B., Derelle, E., Rombauts, S., Bouget, F.-Y., Carre, W., Château, A., Eyre-Walker, A., Grimsley, N., Moreau, H., Piegu, B., Rivals, E., Schackwitz, W., Van de Peer, Y., Piganeau, G. (2014) An improved genome of the model marine alga Ostreococcus tauri unfolds by assessing Illumina de novo assemblies. BMC Genomics 15:1103.


* Piganeau, G., * Vandepoele, K., Gourbiere, S., Van de Peer, Y., Moreau, H. (2009) Unravelling cis-Regulatory Elements in the Genome of the Smallest Photosynthetic Eukaryote: Phylogenetic Footprinting in Ostreococcus. J. Mol. Evol. 69(3):249-59. *contributed equally


John, U., Beszteri, B., Derelle, E., Van de Peer, Y., Read, B., Moreau, H., Cembella, A. (2008) Novel Insights into Evolution of Protistan Polyketide Synthases through Phylogenomic Analysis. Protist 159(1):21-30.


Robbens, S., Derelle, E., Ferraz, C., Wuyts, J., Moreau, H., Van de Peer, Y. (2007) The Complete Chloroplast and Mitochondrial DNA Sequence of Ostreococcus tauri: Organelle Genomes of the Smallest Eukaryote are Examples of Compaction. Mol. Biol. Evol. 24(4):956-68.

Robbens, S., Petersen, J., Brinkmann, H., Rouzé, P., Van de Peer, Y. (2007) Unique regulation of the Calvin cycle in the ultrasmall green alga Ostreococcus. J. Mol. Evol. 64(5):601-4.

Palenik, B., Grimwood, J., Aerts, A., Rouzé, P., Salamov, A., Putnam, N., Zhou, K., Jorgensen, R., Derelle, E., Rombauts, S., Otillar, R., Merchant, S., Podell, S., Gaasterland, T., Manuell, A., Napoli, C., Gendler, K., Vallon, O., Peyretaillade, E., Jancek, S., Piganeau, G., Heijde, M., Jabbari, K., Bowler, C., Werner, G., Robbens, S., Pazour, G., Dubchak, I., Ren, Q., Delwiche, C., Paulsen, I., De Boever, P., Schmutz, J., Rokhsar, D., Van de Peer, Y., Moreau, H., Grigoriev, I. (2007) The Tiny Eukaryote Ostreococcus Provides Genomic Insights Into The Paradox Of Plankton Speciation. Proc. Natl. Acad. Sci. USA 104(18):7705-10.


* Derelle, E., * Ferraz, C., * Rombauts, S., * Rouzé, P., Worden, A.Z., Robbens, S., Partensky, F., Degroeve, S., Echeynie, S., Cooke, R., Saeys, Y., Wuyts, J., Panaud, O., Piegu, B., Ball, S., Ral, J.P., Bouget, F.-Y., Piganeau, G., De Baets, B., Picard, A., Delseny, M., Demaille, J., Van de Peer, Y., Moreau, H. (2006) Genome analysis of the smallest free-living eukaryote Ostreococcus tauri unveils many unique features. Proc. Natl. Acad. Sci. USA 103(31):11647-52. *contributed equally


Robbens, S., Khadaroo, B., Camasses, A., Derelle, E., Ferraz, C., Inzé, D., Van de Peer, Y., Moreau, H. (2005) Genome-wide analysis of core cell cycle genes in the unicellular green alga Ostreococcus tauri. Mol. Biol. Evol. 22(3):589-97.


Khadaroo, B., Robbens, S., Ferraz, C., Derelle, E., Eychenie, S., Cooke, R., Peaucellier, G., Delseny, M., Demaille, J., Van de Peer, Y., Picard, A. (2004) The First Green Lineage cdc25 Dual-Specificity Phosphatase. Cell Cycle 3(4):513-8.

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