Complete Mitochondrial Genome and Phylogenetic Analysis of the Red Algae Chondracanthus tenellus (Rhodophyta, Gigartinales) from South Korea.

Red algae are widely used as a source of health-promoting bioactive compounds and dietary fibers in health foods. The identification and classification of red algal species based on morphological and molecular characteristics is challenging because of the similarity of the thallus and its high degree of plasticity and because complete mitochondrial genomes have only been reported for a few species. In this study, the complete mitochondrial genome sequencing of the red macroalga Chondracanthus tenellus (Harvey) (Hommersand et al., Hydrobiologia 260:105-120, 1993)) (Rhodophyta, Gigartinales) was performed for the first time. Additionally, we aimed to reconstruct the phylogenetic relationships of the species within the order Gigartinales using complete mitochondrial genome sequences. Genomic DNA was extracted, analyzed by whole-genome sequencing (WGS), and assembled using NOVOPlasty. The mitochondrial genome sequence was annotated, and both a genome map and a phylogenetic tree were constructed using maximum likelihood analysis. The mitochondrial genome was 25,928 bp in length, had strongly biased [AT] content (72.08%), and comprised 3 rRNAs, 23 tRNAs, and 24 protein-coding genes (PCGs). In comparison with the mitochondrial genome of other red algae, that of C. tenellus lacks rpl5 and rpl20. Based on a phylogenetic study of the complete mitochondrial genome, C. tenellus belongs to the family Gigartinaceae and is monophyletic with other species of the order Gigartinales. This is the first report of C. tenellus complete mitochondrial genome; its characteristics are consistent with those of other red algae. The study of genomic data will be beneficial for future comparative genomics, phylogenetics, and evolutionary studies.