Deep-water sea anemone with a two-chromosome mitochondrial genome

• Published in: Gene 2019-04, Vol.692, p.195-200
• Main Authors: Dubin, Arseny, Chi, Sylvia Ighem, Emblem, Åse, Moum, Truls, Johansen, Steinar D.
• Format: Article
• Language: English
• Subjects: Actiniaria; Group I intron; Mitochondrial genome rearrangement; Mitochondrial plasmid; mtDNA; Protanthea simplex
• ISSN: 0378-1119; 1879-0038
• DOI: 10.1016/j.gene.2018.12.074

Mitochondrial genome organization of sea anemones appears conserved among species and families, and is represented by a single circular DNA molecule of 17 to 21 kb. The mitochondrial gene content corresponds to the same 13 protein components of the oxidative phosphorylation (OxPhos) system as in vertebrates. Hallmarks, however, include a highly reduced tRNA gene repertoire and the presence of autocatalytic group I introns. Here we demonstrate that the mitochondrial genome of the deep-water sea anemone Protanthea simplex deviates significantly from that of other known sea anemones. The P. simplex mitochondrial genome contains a heavily scrambled order of genes that are coded on both DNA strands and organized along two circular mito-chromosomes, MCh-I and MCh-II. We found MCh-I to be representative of the prototypic sea anemone mitochondrial genome, encoding 12 OxPhos proteins, two ribosomal RNAs, two transfer RNAs, and a group I intron. In contrast, MCh-II was found to be a laterally transferred plasmid-like DNA carrying the conserved cytochrome oxidase II gene and a second allele of the small subunit ribosomal RNA gene. •The mtDNA consists of two circular mito-chromosomes; MCh-I and MCh-II.•MCh-I resembles a typical sea anemone mtDNA, but lacks the CO II gene.•MCh-I gene order is heavily rearranged and both DNA strands contain genes.•MCh-I contains a giant group I intron element of 15 kb within the ND5 gene.•MCh-II provides the CO II gene, and appears laterally transferred.