Construction and comparative analysis of mitochondrial genome in the brown tide forming alga Aureococcus anophagefferens (Pelagophyceae, Ochrophyta)

Aureococcus anophagefferens Hargraves & Sieburth (Pelagophyceae, Ochrophyta) is a marine harmful microalga responsible for brown tides causing significant economic and ecological damage in China, USA, and South Africa. Here, the complete mitochondrial genome of A. anophagefferens strain CCMP 1984 has been constructed and characterized as a 42,401 bp circular-mapping molecule with the A + T content of 65.3%. The mitogenome encompassed 37 protein-coding genes (PCGs), 23 tRNAs, three rRNAs, and six genomic-specific orfs. A group I intron was present in the cox1 gene and encoded an LAGLIDADG homing endonuclease (LHE) in A. anophagefferens. One of the most interesting findings was the presence of three accessory PCGs (dam1, dam2, and dcm) encoding two DNA adenine methyltransferases and a DNA cytosine methyltransferase in the A. anophagefferens mitogenome, which had the nature of microbial origin, indicating that the DNA fragment of virus and bacteria might be obtained via horizontal gene transfer (HGT). This is the first published Pelagophyceae mitogenome, which improves our understanding of its evolutionary history and provides essential genomic information for tracking its ecological dynamics in field investigation on brown tides.