Abstract
The mtDNA of N. tabacum contains 36 protein-coding genes, three ribosomal RNA genes and 21 tRNA genes. We analyzed the potential transcription unit and the post-transcriptional processing of the genes in the tobacco mtDNA. There were 18 gene clusters in tobacco mtDNA with potential cotranscription units based on the relatively short intergenic spacers. The remaining 23 genes would have a monocistronic transcription unit; thus, at least 41 promoters could be postulated in tobacco mtDNA. Nine possible conserved nonanucleotide motif (CNM)-type promoters were found in the upstream regions of atp6, trnfM, nad3, rrn18, nad4L, nad5d, atp1, rps4, and nad7. Therefore, many promoters different from the CNM-type should control mtDNA gene expression in tobacco. We synthesized primers based on tobacco mtDNA sequence, and determined the RNA editing sites by RT-PCR method. We found that RNA editing occurred on 36 kinds of protein-coding genes and the total number of editing sites was 510.
