title: Evolution of pulmonate gastropod mitochondrial genomes: comparisons of gene organizations of Euhadra, Cepaea and Albinaria and implications of unusual tRNA secondary structures.
abstract: Complete gene organizations of the mitochondrial genomes of three pulmonate gastropods, Euhadra herklotsi, Cepaea nemoralis and Albinaria coerulea, permit comparisons of their gene organizations. Euhadra and Cepaea are classified in the same superfamily, Helicoidea, yet they show several differences in the order of tRNA and protein coding genes. Albinaria is distantly related to the other two genera but shares the same gene order in one part of its mitochondrial genome with Euhadra and in another part with Cepaea. Despite their small size (14.1-14.5 kbp), these snail mtDNAs encode 13 protein genes, two rRNA genes and at least 22 tRNA genes. These genomes exhibit several unusual or unique features compared to other published metazoan mitochondrial genomes, including those of other molluscs. Several tRNAs predicted from the DNA sequences possess bizarre structures lacking either the T stem or the D stem, similar to the situation seen in nematode mt-tRNAs. The acceptor stems of many tRNAs show a considerable number of mismatched basepairs, indicating that the RNA editing process recently demonstrated in Euhadra is widespread in the pulmonate gastropods. Strong selection acting on mitochondrial genomes of these animals would have resulted in frequent occurrence of the mismatched basepairs in regions of overlapping genes.
authors.affiliation: Department of Biological Sciences, Faculty of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Yamazaki
authors.forename: R
authors.initials: R
authors.lastname: Ueshima
authors.forename: J A
authors.initials: JA
authors.lastname: Terrett
authors.forename: S
authors.initials: S
authors.lastname: Yokobori
authors.forename: M
authors.initials: M
authors.lastname: Kaifu
authors.forename: R
authors.initials: R
authors.lastname: Segawa
authors.forename: T
authors.initials: T
authors.lastname: Kobayashi
authors.forename: K
authors.initials: K
authors.lastname: Numachi
authors.forename: T
authors.initials: T
authors.lastname: Ueda
authors.forename: K
authors.initials: K
authors.lastname: Nishikawa
authors.forename: K
authors.initials: K
authors.lastname: Watanabe
authors.forename: R H
authors.initials: RH
authors.lastname: Thomas
mesh_terms: D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D004272:DNA, Mitochondrial / Q000235:genetics*; D019143:Evolution, Molecular; D015321:Gene Rearrangement; D016678:Genome; D008969:Molecular Sequence Data; D008974:Mollusca / Q000235:genetics*; D009690:Nucleic Acid Conformation; D017393:RNA Editing; D012343:RNA, Transfer / Q000737:chemistry / Q000235:genetics*
chemical_list: D004272:DNA, Mitochondrial; D012343:RNA, Transfer