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Abstract

Phaeophyceae (brown algae) is a clade of eukaryotic multicellular photosynthetic organisms phylogenetically very distant from the well-studied green lineage. Most brown algal species alternate a diploid sporophytic and a haploid gametophytic phase during their life cycle. However, generation identity is independent of ploidy as, for example, haploid sporophytes can develop through parthenogenesis. Previous studies, in the model species Ectocarpus species 7, identified genes that control the developmental program of the sporophyte generation. In two nearly isomorphic model species Ectocarpus species 7 and Dictyota dichotoma, we used transcriptomic data corresponding to different developmental timepoints to analyse gene co-expression during the life cycle. Furthermore, while most brown algal species possess two life cycle generations, the relative importance and complexity of these generations varies across the brown algal phylogenetic tree. To determine whether generationbiased genes are conserved among brown alga, we analysed RNAseq data from adult stages of ten phylogenetically diverse brown algal species with a high diversity of life cycles.