The First Complete Mitogenome Characterization of Brown Alga Dictyota coriacea (Phaeophyceae, Heterokontophyta) and Its Phylogenetic Analysis

Brown algae (Phaeophyceae) play vital ecological roles in marine ecosystems and are important models for studying organelle genome evolution. Despite their significance, mitogenome data for many taxa remain limited. In this study, we present the complete mitogenome sequence of <i>Dictyota coriacea</i>, a representative brown alga from the family Dictyotaceae (Phaeophyceae). The circular mitogenome of <i>D. coriacea</i> is 31,573 bp in length and encodes 62 genes, including 35 protein-coding genes (PCGs; including uncharacterized open reading frame (<i>orf109</i>)), 25 tRNAs, and 3 rRNAs. The overall gene content and arrangement are largely conserved and consistent with other Dictyotaceae species. However, minor but notable genomic variations were observed, such as gene overlaps, variation in gene lengths, and differences in tRNA gene copy numbers, and the absence of <i>rpl31</i>. All PCGs use standard start and stop codons, with most initiating with ATG and terminating with TAA, TAG, or TGA. Phylogenetic analysis confirmed <i>D. coriacea's</i> close relationship with <i>D. dichotoma</i>, <i>Dictyopteris divaricata</i>, and <i>Dictyotopsis propagulifera</i>, supporting its taxonomic placement. This study's findings improve our understanding of algae evolution and provide useful genetic markers for future research on evolutionary relationships and species classification within this group of algae.