title: First comparative insight into the architecture of COI mitochondrial minicircle molecules of dicyemids reveals marked inter-species variation.
abstract: Dicyemids, poorly known parasites of benthic cephalopods, are one of the few phyla in which mitochondrial (mt) genome architecture departs from the typical ~16 kb circular metazoan genome. In addition to a putative circular genome, a series of mt minicircles that each comprises the mt encoded units (I-III) of the cytochrome c oxidase complex have been reported. Whether the structure of the mt minicircles is a consistent feature among dicyemid species is unknown. Here we analyse the complete cytochrome c oxidase subunit I (COI) minicircle molecule, containing the COI gene and an associated non-coding region (NCR), for ten dicyemid species, allowing for first time comparisons between species of minicircle architecture, NCR function and inferences of minicircle replication. Divergence in COI nucleotide sequences between dicyemid species was high (average net divergence = 31.6%) while within species diversity was lower (average net divergence = 0.2%). The NCR and putative 5' section of the COI gene were highly divergent between dicyemid species (average net nucleotide divergence of putative 5' COI section = 61.1%). No tRNA genes were found in the NCR, although palindrome sequences with the potential to form stem-loop structures were identified in some species, which may play a role in transcription or other biological processes.
authors: School of Biological Sciences,University of Adelaide,Adelaide SA 5005,Australia.
authors: Sarah R
authors: SR
authors: Catalano
authors: Parasitology Section,South Australian Museum,Adelaide SA 5000,Australia.
authors: Ian D
authors: ID
authors: Whittington
authors: Australian Centre for Evolutionary Biology and Biodiversity,University of Adelaide,Adelaide SA 5005,Australia.
authors: Stephen C
authors: SC
authors: Donnellan
authors: School of Biological Sciences,University of Adelaide,Adelaide SA 5005,Australia.
authors: Terry
authors: T
authors: Bertozzi
authors: School of Biological Sciences,University of Adelaide,Adelaide SA 5005,Australia.
authors: Bronwyn M
authors: BM
authors: Gillanders
mesh_terms: D000818:Animals; D001483:Base Sequence; D049830:Cephalopoda / Q000469:parasitology*; D004272:DNA, Mitochondrial / Q000235:genetics; D003576:Electron Transport Complex IV / Q000235:genetics; D014644:Genetic Variation; D054629:Genome, Mitochondrial / Q000235:genetics*; D007448:Invertebrates / Q000145:classification* / Q000201:enzymology / Q000235:genetics; D008928:Mitochondria / Q000201:enzymology / Q000235:genetics; D008969:Molecular Sequence Data; D010802:Phylogeny; D022661:RNA, Untranslated / Q000235:genetics; D016415:Sequence Alignment / Q000662:veterinary; D017422:Sequence Analysis, DNA / Q000662:veterinary; D013045:Species Specificity
chemical_list: D004272:DNA, Mitochondrial; D022661:RNA, Untranslated; D003576:Electron Transport Complex IV
keywords: Dicyemida; cytochrome c oxidase; minicircle molecules; mitochondrial DNA; multi-species phylogenetic comparisons; taxonomic classification