The complete mitochondrial genome and phylogenetic analysis of Coscinodiscus wailesii (Coscinodiscophyceae, Bacillariophyta)

Coscinodiscus is a species-rich genus with about 400 species described, many of which are harmful algal bloom species with significant negative ecological impact. Despite of their importance in primary production and as harmful algal bloom species, genome data for species in this genus is limited. No mitochondrial genome (mtDNA) of any species in this genus has been reported. Here, the complete mtDNA sequence of the Coscinodiscus wailesii Gran & Angst 1931 was constructed and analyzed. The circular mtDNA was 36,071 bp in length, encoding 64 genes, including 34 protein coding genes (PCGs), 24 transfer RNA (tRNA) genes, 2 ribosomal RNA (rRNA) genes and 4 conserved open reading frames (orfs). The overall AT content of C. wailesii mtDNA was 75.00%, which was slightly lower than that of Melosira undulate (78.40%). Maximum likelihood (ML) phylogenetic analysis using 29 shared protein-coding genes revealed that C. wailesii clustered well with M. undulata, which was the only species of class Coscinodiscophyceae whose mtDNA has been fully constructed. The complete mtDNAs of more Coscinodiscus species will be valuable for studying the evolutionary relationships among species in the genus Coscinodiscus and in the Class of Coscinodiscophyceae.