Complete mitochondrial genome of Thalassiosira profunda (Mediophyceae, Bacillariophyta)

Thalassiosira is a species-rich genus with about 170 described species, many of which are harmful algal species with significant negative ecological impact. However, genome data of these species remain limited. In this study, the complete mitochondrial genome of Thalassiosira profunda (Hendey) Hasle 1973 was determined for the first time. The circular genome was 40,470 bp in length with GC content of 30.98%. It encodes 63 genes including 36 protein-coding genes (PCGs), 25 tRNA genes, and two rRNA genes. Phylogenetic analysis using concatenated PCGs suggested that T. profunda had a closer evolutionary relationship with Skeletonema marinoi of a different family (Skeletonemataceae) than Thalassiosira pseudonana, suggesting complex evolutionary relationship among species in these two families. Colinearity analysis also revealed fewer genome rearrangements between T. profunda and S. marinoi than that between T. profunda and T. pseudonana. This study suggests that mitochondrial genomes of many more species in the Thalassiosiraceae and Skeletonemataceae families are needed to disentangle the complex evolutionary relationships in the order of Thalassiosirales.