Nakazono M, Ito Y, Tsutsumi N, Hirai A
Laboratory of Radiation Genetics, Faculty of Agriculture, University of Tokyo, 1-1-1 Yayoi, Bunkyo, Tokyo 113, Japan.
Curr Genet. 1996 Apr;29(5):412-6. doi: 10.1007/BF02221507.
We previously identified a chloroplast-derived (ct-derived) sequence of 32 base pairs (bp) in rice mitochondrial DNA that includes a part (30 bp; psitrnI) of a gene for isoleucine tRNA (CAU) of the chloroplast. Analyzing the ct-derived psitrnI, we found that an open reading frame (orf240), which was homologous to the gene for a subunit of an ATP-binding cassette-type (ABC-type) heme transporter, namely helC, of Rhodobacter capsulatus, and a gene for subunit 6 of NADH dehydrogenase (nad6) were located upstream of and downstream from the ct-derived psitrnI, respectively. Northern-blot hybridization and analysis by reverse transcription-polymerase chain reaction (RT-PCR) revealed that both orf240 and nad6 were co-transcribed in rice mitochondria. An analysis of PCR-amplified fragments of the region of orf240/nad6 from the DNA of some Gramineae suggests that the arrangement of orf240/nad6 was generated in the mitochondrial genome of the genus Oryza during evolution after its divergence from the other Gramineae. Most of the transcripts of orf240 are edited, with a change from cytidine to uridine, at 35 positions. Editing of the RNA changes 33 amino-acid residues among the 240 encoded amino-acid residues, suggesting that the orf240 gene is functional in rice mitochondria.
我们之前在水稻线粒体DNA中鉴定出一段32个碱基对（bp）的叶绿体衍生（ct衍生）序列，其中包含叶绿体异亮氨酸tRNA（CAU）基因的一部分（30 bp；psitrnI）。通过分析ct衍生的psitrnI，我们发现一个开放阅读框（orf240），它与荚膜红细菌ATP结合盒式（ABC型）血红素转运蛋白一个亚基的基因（即helC）同源，以及一个NADH脱氢酶亚基6（nad6）的基因，分别位于ct衍生的psitrnI的上游和下游。Northern杂交和逆转录聚合酶链反应（RT-PCR）分析表明，orf240和nad6在水稻线粒体中共同转录。对一些禾本科植物DNA中orf240/nad6区域的PCR扩增片段分析表明，orf240/nad6的排列是在稻属线粒体基因组从其他禾本科植物分化后的进化过程中产生的。orf240的大多数转录本在35个位置发生编辑，胞嘧啶变为尿嘧啶。RNA的编辑在240个编码氨基酸残基中改变了33个氨基酸残基，这表明orf240基因在水稻线粒体中具有功能。
