Brown algae are interesting for many reasons, both scientific and economic, including their phylogenetic position, their complex multicellularity evolution independent of terrestrial animals and plants, their chloroplasts derived from secondary endosymbiosis, and the production of novel biomolecules. The filamentous brown alga Ectocarpus sp. was chosen as a model species for this group for its small size, its relatively short life cycle (2-3 months, possible control in laboratory), its high fertility, the ease of genetic cross-breeding and finally, the relatively small size of its genome. A range of genetic, molecular and cellular tools has been established for this organism, including a very good quality genome assembly. In addition, mutant lines can be created by mutagenesis and mutations identified by several approaches.
Diploid sporophytes produce meiospores (haploid spores produced by meiosis) in unilocular sporangia. The meiospores develop into male and female gametophytes (dioecious), which in turn produce gametes in plurilocular gametangles. Male and female gametes appear to be morphologically almost identical but differ physiologically and in their behaviour: female gametes are released into the water earlier and emit a pheromone; male gametes swim longer and are attracted by the pheromone.
Gamete fusion produces a zygote that develops into a diploid sporophyte, thus completing the life cycle.
Unfused gametes can form a parthenosporophyte, morphologically identical to a diploid sporophyte. Sporophytes and parthenosporophytes can reproduce asexually by producing mito-spores in plurilocular sporangia.
« Proposal of Ectocarpus siliculosus as a model organism for brown algal genetics and genomics », Peters, A.F., Marie, D., Scornet, D., Kloareg, B. and Cock, J.M., Journal of Phycology, 2004
« The Ectocarpus genome and the independent evolution of multicellularity in brown algae », Cock, J.M., et al., Nature, 2010
« Re-annotation, improved large-scale assembly and establishment of a catalogue of non-coding loci for the genome of the model brown alga Ectocarpus », Cormier, A., Avia, K., Sterck, L., Derrien, T., Wucher, V., Andres, G., Monsoor, M., Godfroy, O, Lipinska, A., Perrineau, M.-M., Van De Peer, Y., Hitte, C., Corre, E., Coelho, S.M. and Cock, J.M., New Phytologist, 2017
« The Ectocarpus IMMEDIATE UPRIGHT gene encodes a member of a novel family of cysteine-rich proteins with an unusual distribution across the eukaryotes », Macaisne, N., Liu, F., Scornet, D., Peters, A.F., Lipinska, A., Perrineau, M.M.P., Henry, A., Strittmatter, M., Coelho, S.M. and Cock, J.M., Development, 2017
« Convergent recruitment of TALE homeodomain life cycle regulators to direct sporophyte development in land plants and brown algae », Arun, A., Coelho, S.M., Peters, A.F., Bourdareau, S., Pérès, L., Scornet, D., Strittmatter, M., Lipinska, A.P., Yao, H., Godfroy, O., Montecinos, G.J., Avia, K., Macaisne, N., Troadec, C., Bendahmane, A. and Cock J.M. ,eLife, 2019
« Histone modifications during the life cycle of the brown alga Ectocarpus », Bourdareau, S., Tirichine, L., Lombard, B., Loew, D., Coelho, S.M. and Cock, J.M., bioRxiv, 2020
« High-density genetic map and identification of QTLs for responses to high temperature and low salinity stresses in the model alga Ectocarpus sp. », Avia, K., Coelho, S.M., Montecinos, G.J., Cormier, A., Lerck, F., Mauger, S., Faugeron, S., Valero, M., Cock, J.M. and Boudry, P., Scientific Reports, 2017
« microRNAs and the evolution of complex multicellularity: identification of a large, diverse complement of microRNAs in the brown alga Ectocarpus », Tarver, J., Cormier, A. Pinzon, N., Taylor, R., Carré, W., Strittmatter, M., Seitz, H., Coelho, S.M. and Cock, J.M., Nucleic Acids Research, 2015
« A haploid system of sex determination in the brown alga Ectocarpus sp. », Ahmed, S., Cock, J.M., Pessia, E., Luthringer, R., Cormier, A., Robuchon, M. Sterck, L., Peters, A.F., Dittami, S.M., Corre, E., Valero, M., Aury, J.-M., Roze, D., Van de Peer, Y., Bothwell, J., Marais, G.A.B., Coelho, S.M., Current Biology, 2014