Journal of Molecular Evolution

, Volume 34, Issue 4, pp 331–335 | Cite as

Planarian mitochondria II. The unique genetic code as deduced from cytochrome c oxidase subunit I gene sequences

  • Yoshitaka Bessho
  • Takeshi Ohama
  • Syozo Osawa


The cytochrome c oxidase subunit I (COI) gene sequences from planarian (Dugesia japonica) DNA, most probably of mitochondrial origin, are heterogeneous. Taking advantage of the heterogeneity that occurs primarily in silent sites of the COI DNA sequences, amino acid assignments of several codons have been deduced as nonuniversal: UGA = Trp, AAA = Asp, and AGR (R: A or G) = Ser. In addition, UAA, a stop codon in the universal genetic code, is tentatively assumed to be a tyrosine codon, because three of the sequences examined have UAA at the well-conserved tyrosine site of UAY (Y: U or C) in other planarian sequences as well as in the mitochondria of human, Xenopus, sea urchin, Drosophila, Trypanosoma, and Saccharomyces cerevisiae. AUA would most probably be an isoleucine codon in these mitochondria, whereas it is a methionine codon in the majority of nonplant mitochondria.

Key words

Genetic code Mitochondria Planarian Dugesia japonica Cytochrome c oxidase subunit I gene UAA tyrosine codon 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Anderson S, Bankier AT, Barrell BG, de Bruijn MHL, Coulson AR, Drouin J, Eperon IC, Nierlich DP, Roe BA, Sanger F, Schreier PH, Smith ALH, Staden R, Young IG (1981) Sequence and organization of the human mitochondrial genome. Nature 290:457–464Google Scholar
  2. Bessho Y, Ohama T, Osawa S (1992) Planarian mitochondria I. Heterogeneity of cytochrome c oxidase subunit I gene sequences in the freshwater planarian, Dugesia japonica. J Mol Evol 34:000–000Google Scholar
  3. Bonitz SG, Coruzzi G, Thalenfeld BE, Tzagoloff A, Macino G (1980) Assembly of the mitochondrial membrane system: structure and nucleotide sequence of the gene coding for subunit I of yeast cytochrome oxidase. J Biol Chem 255:11927–11941Google Scholar
  4. Cantatore P, Roberti M, Rainaldi G, Gadaleta MN, Saccone C (1989) The complete nucleotide sequence, gene organization, and genetic code of the mitochondrial genome of Paracentrotus lividus. J Biol Chem 264:10965–10975Google Scholar
  5. Cattaneo R (1990) Messenger RNA editing and the genetic code. Experientia 46:1142–1148Google Scholar
  6. Clary DO, Wolstenholme DR (1985) The mitochondrial DNA molecule of Drosophila yakuba: nucleotide sequence, gene organization, and genetic code. J Mol Evol 22:252–271Google Scholar
  7. Garey JR, Wolstenholme DR (1989) Platyhelminth mitochondrial DNA: evidence for early evolutionary origin of tRNAser AGN that contains a dihydrouridine arm replacement loop, and serine-specifying AGA and AGG codons. J Mol Evol 28: 374–387Google Scholar
  8. Hensgens LAM, Brakenhoff J, de Vries BF, Sloof P, Tromp MC, van Boom JH, Benne R (1984) The sequence of the gene for cytochrome c oxidase subunit I, a frameshift containing gene for cytochrome c oxidase subunit II and seven unassigned reading frames in Trypanosoma brucei mitochondrial maxi-circle DNA. Nucleic Acids Res 12:7327–7344Google Scholar
  9. Himeno H, Masaki H, Kawai T, Ohta T, Kumagai I, Miura I, Watanabe K (1987) Unusual genetic codes and a novel gene structure for tRNAAAGY Ser in starfish mitochondrial DNA. Gene 56:219–230Google Scholar
  10. Jacobs HT, Elliot DJ, Math VB, Farquharson A (1988) Nucleotide sequence and gene organization of sea urchin mitochondrial DNA. J Mol Biol 202:185–217Google Scholar
  11. Jukes TH, Osawa S (1990) The genetic code in mitochondria and chloroplasts. Experientia 46:1117–1126Google Scholar
  12. Ohama T, Osawa S, Watanabe K, Jukes TH (1990) Evolution of the mitochondrial genetic code IV: AAA as an asparagine codon in some animal mitochondria. J Mol Evol 30:329–332Google Scholar
  13. Roe BA, Ma DP, Wilson RK, Wong JFH (1985) The complete nucleotide sequence of the Xenopus laevis mitochondrial genome. J Biol Chem 260:9759–9774Google Scholar

Copyright information

© Springer-Verlag New York Inc 1992

Authors and Affiliations

  • Yoshitaka Bessho
    • 1
  • Takeshi Ohama
    • 1
  • Syozo Osawa
    • 1
  1. 1.Laboratory of Molecular Genetics, Department of Biology, School of ScienceNagoya UniversityChikusa-ku, NagoyaJapan

Personalised recommendations