Epigenetics in Algae

Algae are ancient organisms closely associated with bacteria and plants. Collectively, they are comprised of photosynthetic multi- and unicellular aquatic species. Algae have extraordinary genetic and biological diversity and have been found in almost every ecological niche around the world, reflecting a wide range of environmental adaptations. There are anywhere from 40,000 to over one million algae species. Tremendous effort has been made to sequence algae genomes, particularly for those species that are important for the bioeconomy. However, to date, only 20 algae species have been assessed for either DNA or histone modifications. From these studies, we have learned that the phylogenetic and genomic diversity of algae is reflected in the quantity, distribution, localization, and function of their epigenetic modifications. Indeed, different epigenetic strategies are employed by different alga; this epigenetic diversity may help elucidate the mechanisms of the evolution of epigenetic processes. While common patterns are lacking, most algae have conserved histone modifications and DNA methylation similar to plants; however, epigenomic assessment of more species is needed to discern an algal "epigenetic code." Finally, algae contribute to 40% of the global primary production, including playing a significant role in the global carbon sink. Perturbation of environmental factors alters the epigenome in select algae species, resulting in significant changes to productivity. It is paramount that we develop a deeper understanding of gene-by-environment interactions, specifically epigenetic regulation of algae lifecycles, to determine the effects of climate change on algae physiology and the resulting reciprocal impact on climate change.