Rice Mitochondrial Genome : Studies on the complete sequence, expression and post transcriptional regulation.

水稻（Oryza sativa L.）的整个线粒体基因组，一种单子叶植物，已经被测序。该基因全长490，520 bp，平均G+C含量为43.8%。鉴定了3个rRNA基因、17个tRNA基因和5个假tRNA序列。此外，还发现了11个核糖体蛋白基因和2个假核糖体蛋白基因，它们与地钱线粒体基因组中16个核糖体蛋白基因中的13个同源。在水稻、拟南芥和甜菜的核糖体蛋白基因和tRNA基因中，观察到基因的存在/不存在和完整性方面的更大程度的变化。还检查了水稻线粒体序列中的转录和转录后修饰（RNA编辑）。基因组DNA中共有491个Cs转化为cDNA中的Ts。RNA编辑的频率根据所考虑的ORF而显著不同。来自质体和核基因组的序列分别占线粒体基因组的6.3%和13.4%。线粒体基因组中质体序列的保守程度在61%到100%之间，表明序列迁移非常频繁。三个质体DNA片段，被纳入线粒体基因组，随后转移到核基因组。鉴定了19个与转座子或反转录转座子序列相似，但与双子叶植物线粒体基因组中发现的片段不同的片段。结果表明，频繁和独立的DNA序列流和线粒体基因组在开花植物的进化过程中，这可能是解释的范围内观察到的高等植物的线粒体基因组之间的遗传变异。

The entire mitochondrial genome of rice (Oryza saliva L.), a monocot plant, has been sequenced. It was found to comprise 490,520 bp, with an average G+C content of43.8%. 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.