Single-base methylome profiling of the giant kelp Saccharina japonica reveals significant differences in DNA methylation to plants and animals

Kelp are the largest photosynthetic organisms in the ocean with tissue differentiation and complex life cycles. Other multicellular organisms with similar complexity such as plants and animals are well known to posses epigenetic mechanisms such as DNA methylation to control development and morphogenesis. Despite plant-like body plans and the presence of different life-cycle stages, the kelp species Saccharina japonica has only a very low level of DNA methylation, yet we have found strong evidence for differential methylation of regulatory elements and protein-coding genes which seem to contribute to the formation of life-cycle stages, tissue differentiation, growth and halogen metabolism. Thus, DNA methylation seems to play an important role in kelp, which has not been reported before. We generated bisulfite treated genomic DNA sequencing from male, female haploid gametophytes and diploid sporophytes of S. japonica.