Created 20/01/2021
20 Jan
2021
Histone modifications during the life cycle of the brown alga Ectocarpus. Genome Biology, 22, 12.

Bourdareau, S., Tirichine, L., Lombard, B., Loew, D., Wu, Y., Coelho, S.M. and Cock, J.M. (2020). https://doi.org/10.1186/s13059-020-02216-8

Brown algae evolved complex multicellularity independently of the animal and land plant lineages and are the third most developmentally complex phylogenetic group on the planet. An understanding of developmental processes in this group is expected to provide important insights into the evolutionary events necessary for the emergence of complex multicellularity. Epigenetic regulation of gene expression during development is mediated by a complex network of processes involving many components of the cellular machinery including modifications of the chromatin structure of the chromosomes. This study represents the first analysis in a macroalga of a key component of chromatin regulation, post-translational modifications (PTMs) of histone proteins. The study included an extensive census of histone PTMs in the model brown alga Ectocarpus together with an analysis of the genome-wide distribution of eight PTMs using a ChIP-seq approach. These included PTMs associated with the transcriptional start sites and gene bodies of active genes, PTMs associated with repeated sequences and a PTM, H3K79me2, that exhibited an unusual pattern of distribution that has not been observed in organisms from other lineages. Interestingly, Ectocarpus lacks both H3K27me3 and the major polycomb complexes. The overview of histone PTMs in the brown algae obtained by this study will provide a foundation for future studies aimed at understanding the role of chromatin modifications in the regulation of brown algal genomes.

Brown algae evolved complex multicellularity independently of the animal and land plant lineages and are the third most developmentally complex phylogenetic group on the planet. An understanding of developmental processes in this group is expected to provide important insights into the evolutionary events necessary for the emergence of complex multicellularity. Epigenetic regulation of gene expression during development is mediated by a complex network of processes involving many components of the cellular machinery including modifications of the chromatin structure of the chromosomes. This study represents the first analysis in a macroalga of a key component of chromatin regulation, post-translational modifications (PTMs) of histone proteins. The study included an extensive census of histone PTMs in the model brown alga Ectocarpus together with an analysis of the genome-wide distribution of eight PTMs using a ChIP-seq approach. These included PTMs associated with the transcriptional start sites and gene bodies of active genes, PTMs associated with repeated sequences and a PTM, H3K79me2, that exhibited an unusual pattern of distribution that has not been observed in organisms from other lineages. Interestingly, Ectocarpus lacks both H3K27me3 and the major polycomb complexes. The overview of histone PTMs in the brown algae obtained by this study will provide a foundation for future studies aimed at understanding the role of chromatin modifications in the regulation of brown algal genomes.

 

ChIP-seq: Example region of the genome showing the distribution of eight chromatin post-translational modifications in sporophytes 5SP) and gametophytes (GA).

 

Polycomb: Brown algae lack the major polycomb complexes (PRC1 and PRC2)