Nakazono M, Itadani H, Wakasugi T, Tsutsumi N, Sugiura M, Hirai A
Laboratory of Radiation Genetics, Faculty of Agriculture, University of Tokyo, Japan.
Curr Genet. 1995 Jan;27(2):184-9. doi: 10.1007/BF00313433.
The two gene clusters rps3-rpl16 and nad3-rps12 are separated from each other in the mitochondrial genome and are expressed as the individual transcription units in many plants. In rice mitochondrial DNA (mtDNA), the four genes rps3, rpl16, nad3 and rps12 are located within a region of 6 kbp. Northern-blot analysis revealed that a large transcript (6.6 kb) hybridized to both the rps3-rpl16 and the nad3-rps12 gene clusters. Using RT-PCR, we amplified a fragment of anticipated size (790 bp) from two primers that corresponded to sequences in the coding regions of rpl16 and nad3, demonstrating that at least two of the four genes, namely rpl16 and nad3, were co-transcribed. These results together indicated that all four genes, namely, rps3, rpl16, nad3 and rps12, were co-transcribed in rice mitochondria. Transcription initiation sites were determined by an in vitro capping/ribonuclease protection assay and primer extension analysis. Two initiation sites were identified in the rps3-rpl16-nad3-rps12 gene cluster: one was located upstream of rps3 and the other was located between rpl16 and nad3. This evidence indicates that the rps3-rpl16-nad3-rps12 gene cluster is transcribed from two alternative promoters.
两个基因簇rps3 - rpl16和nad3 - rps12在线粒体基因组中彼此分离，并且在许多植物中作为独立的转录单元表达。在水稻线粒体DNA（mtDNA）中，rps3、rpl16、nad3和rps12这四个基因位于6 kbp的区域内。Northern杂交分析显示，一个大转录本（6.6 kb）与rps3 - rpl16和nad3 - rps12基因簇均杂交。使用RT - PCR，我们从对应于rpl16和nad3编码区序列的两个引物中扩增出预期大小（790 bp）的片段，证明四个基因中至少有两个，即rpl16和nad3，是共转录的。这些结果共同表明，rps3、rpl16、nad3和rps12这四个基因在水稻线粒体中是共转录的。转录起始位点通过体外加帽/核糖核酸酶保护试验和引物延伸分析来确定。在rps3 - rpl16 - nad3 - rps12基因簇中鉴定出两个起始位点：一个位于rps3上游，另一个位于rpl16和nad3之间。这一证据表明rps3 - rpl16 - nad3 - rps12基因簇是从两个交替启动子转录而来的。
