Kohchi T, Ogura Y, Umesono K, Yamada Y, Komano T, Ozeki H, Ohyama K
Research Center for Cell and Tissue Culture, Faculty of Agriculture, Kyoto University, Japan.
Curr Genet. 1988 Aug;14(2):147-54. doi: 10.1007/BF00569338.
From the complete sequence of the chloroplast DNA in a liverwort, Marchantia polymorpha, an unidentified open reading frame, ORF203, was found between the psbB and rps12' (trans-split) genes. ORF203 was a split gene consisting of three exons and two group II introns. Multiple transcripts for ORF203 were detected on Northern blots of the chloroplast RNA preparation. The ORF203 locus was primarily co-transcribed with the downstream genes rps12' and rpl20, and then processed into a monomeric precursor. S1 nuclease mapping gave the transcription initiation site 52 nucleotides upstream from the coding sequence of ORF203. The spliced RNA molecules were identified, as predicted, by the use of synthetic oligodeoxyribonucleotide probes specific to ligated exon sequences. The splicing reaction proceeded successively from the 5' to 3' direction. These results indicate that ordered RNA processing occurs in the chloroplast of land plants. Trans-membrane analysis by a computer indicated that ORF203 gene product could be associated with a chloroplast membrane.
在一种苔类植物——地钱（Marchantia polymorpha）的叶绿体DNA完整序列中，在psbB基因和rps12'（跨剪接）基因之间发现了一个未鉴定的开放阅读框ORF203。ORF203是一个由三个外显子和两个II类内含子组成的断裂基因。在叶绿体RNA制备物的Northern印迹上检测到了ORF203的多个转录本。ORF203基因座主要与下游基因rps12'和rpl20共同转录，然后加工成单体前体。S1核酸酶图谱分析确定转录起始位点位于ORF203编码序列上游52个核苷酸处。通过使用针对连接外显子序列的合成寡脱氧核糖核苷酸探针，如预测的那样鉴定出了剪接后的RNA分子。剪接反应从5'向3'方向依次进行。这些结果表明陆地植物叶绿体中发生了有序的RNA加工。通过计算机进行的跨膜分析表明，ORF203基因产物可能与叶绿体膜相关。
