A draft genome of the brown alga, Cladosiphon okamuranus, S-strain: a platform for future studies of ‘mozuku’ biology

The brown alga, Cladosiphon okamuranus (Okinawa mozuku), is economically one of the most important edible seaweeds, and is cultivated for market primarily in Okinawa, Japan. C. okamuranus constitutes a significant source of fucoidan, which has various physiological and biological activities. To facilitate studies of seaweed biology, we decoded the draft genome of C. okamuranus S-strain. The genome size of C. okamuranus was estimated as ∼140 Mbp, smaller than genomes of two other brown algae, Ectocarpus siliculosus and Saccharina japonica. Sequencing with ∼100× coverage yielded an assembly of 541 scaffolds with N50 = 416 kbp. Together with transcriptomic data, we estimated that the C. okamuranus genome contains 13,640 protein-coding genes, approximately 94% of which have been confirmed with corresponding mRNAs. Comparisons with the E. siliculosus genome identified a set of C. okamuranus genes that encode enzymes involved in biosynthetic pathways for sulfated fucans and alginate biosynthesis. In addition, we identified C. okamuranus genes for enzymes involved in phlorotannin biosynthesis. The present decoding of the Cladosiphon okamuranus genome provides a platform for future studies of mozuku biology.