Résumé
The complete nucleotide sequence of the Chlamydomonas eugametos (Chlamydomonadales, Chlorophyceae, sensu Mattox and Stewart) mitochondrial genome has been determined (22 897 bp, 34.6% G + C). The genes identified in this circular-mapping genome include those for apocytochrome b, subunit 1 of the cytochrome oxidase complex, subunits 1,2,4,5, and 6 of the NADH dehydogenase complex, discontinuous large and small subunit ribosomal rRNAs and three tRNAs whose anticodons CAU, CCA and UUG are specific for methione, tryptophan and glutamine, respectively. The C. eugametos mitochondral DNA (mtDNA), therefore, shares almost the same reduced set of coding functions and similar unusual features of rRNA gene organization with the linear 15.8 kb mtDNA of Chlamydomonas reinhardtii, the only other completely sequenced chlamydomonadalean mtDNA. However, sequence analysis of the C. eugametos mtDNA has revealed the following distinguishing features relative to those of C. reinhardtii: (1) the absence of a reverse transcriptase-like gene homologue, (2) the presence of an additional gene for tRNA(met) that may be a pseudogene, (3) a completely different gene order, (4) transcription of all genes from the same mtDNA strand, (5) a lower G + C content, (6) less pronounced bias in codon usage, and (7) nine group I introns, several of which contain open reading frames coding for potential maturases/endonucleases and two have a nucleotide at the 5' or 3' splice site of the deduced precursor RNAs that deviates from highly conserved nucleotides reported in other group I introns. The features of mitochondrial genome organization and gene content shared by C. eugametos and C. reinhardtii contrast with those of other green algal mtDNAs that have been characterized in detail. The deep evolutionary divergence between these two Chlamydomonas taxa within the Chlamydomonadales suggests that their shared features of mitochondrial genome organization evolved prior to the origin of this group.
| Langue d'origine | English |
|---|---|
| Pages (de-à) | 285-295 |
| Nombre de pages | 11 |
| Journal | Plant Molecular Biology |
| Volume | 36 |
| Numéro de publication | 2 |
| DOI | |
| Statut de publication | Published - janv. 1998 |
Note bibliographique
Funding Information:This work was supported by a Natural Sciences and Engineering Research Council of Canada (NSERC) grant to R.W.L., E.M.D.-W. and A.M.N. were Izaak Walton Killam Scholars and E.M.D.-W. was also an NSERC post-graduate scholar. We would like to thank Michael Gray and Murray Schnare for helpful discussion, Michael Gray for critically reading an earlier version of the manuscript, Francois Michel for information on atypical group I intron splice-sites, Christoph Sensen and Clayton Knight for assistance in data analysis, Kelly Prendergast for editing the manuscript and Gertraud Burger for help with gene nomenclature. Tamara Western, as an Honours BSc student in the laboratory of R.W.L., performed the sequencing and analysis of the 2.5 kb HindIII fragment of C. moewusii mtDNA cited in this paper.
ASJC Scopus Subject Areas
- Agronomy and Crop Science
- Genetics
- Plant Science