Organelle genomes of Sargassum confusum (Fucales, Phaeophyceae): mtDNA vs cpDNA

Abstract

The drifting biomass of golden tide in the Yellow Sea of China mainly consisted of Sargassum horneri with a small fraction composed of Sargassum confusum thalli. In this study, the circular-mapping organelle genomes (mtDNA and cpDNA) of S. confusum were sequenced and coupled with comparative genomic and phylogenomic analyses within the Sargassum genus. This revealed 34,721-bp mitochondrial and 124,375-bp chloroplast genomes of S. confusum harboring 65 and 173 genes, respectively, figures which are highly comparable to those reported in other Sargassum species. The mtDNA of S. confusum displayed lower values in A+T and intergenic spacer contents than cpDNA. Mitochondrial phylogenomics revealed a close relationship between Sargassum muticum and S. confusum. The Sargassum mtDNAs had an approximately three-fold greater mutation rate than cpDNAs indicating a higher evolution rate in mtDNAs than cpDNAs for Sargassum species. Therefore, mtDNA is a more effective molecular marker and could aid in tracking the source of the golden tides.