title: The complete sequence of the rice (Oryza sativa L.) mitochondrial genome: frequent DNA sequence acquisition and loss during the evolution of flowering plants.
abstract: The entire mitochondrial genome of rice (Oryza sativa L.), a monocot plant, has been sequenced. It was found to comprise 490,520 bp, with an average G+C content of 43.8%. Three rRNA genes, 17 tRNA genes and five pseudo tRNA sequences were identified. In addition, eleven ribosomal protein genes and two pseudo ribosomal protein genes were found, which are homologous to 13 of the 16 genes for ribosomal proteins in the mitochondrial genome of the liverwort (Marchantia polymorpha). A greater degree of variation in terms of presence/absence and integrity of genes was observed among the ribosomal protein genes and tRNA genes of rice, Arabidopsis and sugar beet. Transcription and post-transcriptional modification (RNA editing) in the rice mitochondrial sequence were also examined. In all, 491 Cs in the genomic DNA were converted to Ts in cDNA. The frequency of RNA editing differed markedly depending upon the ORF considered. Sequences derived from plastid and nuclear genomes make up 6.3% and 13.4% of the mitochondrial genome, respectively. The degree of conservation of plastid sequences in the mitochondrial genome ranged from 61% to 100%, suggesting that sequence migration has occurred very frequently. Three plastid DNA fragments that were incorporated into the mitochondrial genome were subsequently transferred to the nuclear genome. Nineteen fragments that were similar to transposon or retrotransposon sequences, but different from those found in the mitochondrial genomes of dicots, were identified. The results indicate frequent and independent DNA sequence flow to and from the mitochondrial genome during the evolution of flowering plants, and this may account for the range of genetic variation observed between the mitochondrial genomes of higher plants.
authors.affiliation: Department of Genetic Diversity, National Institute of Agrobiological Sciences, Kannondai 2-1-2, Tsukuba, Ibaraki 305-8602, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Notsu
authors.forename: S
authors.initials: S
authors.lastname: Masood
authors.forename: T
authors.initials: T
authors.lastname: Nishikawa
authors.forename: N
authors.initials: N
authors.lastname: Kubo
authors.forename: G
authors.initials: G
authors.lastname: Akiduki
authors.forename: M
authors.initials: M
authors.lastname: Nakazono
authors.forename: A
authors.initials: A
authors.lastname: Hirai
authors.forename: K
authors.initials: K
authors.lastname: Kadowaki
mesh_terms: D005075:Biological Evolution; D002467:Cell Nucleus / Q000235:genetics; D004251:DNA Transposable Elements; D004272:DNA, Mitochondrial / Q000235:genetics*; D035263:Flowering Tops / Q000235:genetics; D017343:Genes, Plant / Q000235:genetics*; D018745:Genome, Plant; D008928:Mitochondria / Q000235:genetics*; D008969:Molecular Sequence Data; D012275:Oryza / Q000235:genetics*; D018087:Plastids / Q000235:genetics; D017393:RNA Editing; D012343:RNA, Transfer / Q000235:genetics; D011995:Recombination, Genetic; D018626:Retroelements
chemical_list: D004251:DNA Transposable Elements; D004272:DNA, Mitochondrial; D018626:Retroelements; D012343:RNA, Transfer