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KMID : 0578319940040010111
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Molecules and Cells
1994 Volume.4 No. 1 p.111 ~ p.118
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Isolation and characterization of The Cytochrome Oxidase Subunit I Gene (coI) from rice mitochondira
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Moon Eunpyo
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Abstract
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I have isolated and analyzed the co/ gene from rice (Oryza saliva) mitochondria. The 1575 by protein coding region shares extensive sequence identity at the nucleotide level to the col genes from maize (99.9%) and peas (93.9%). One CGG codon is present which probably codes tryptophan rather than arginine by being changed to TGG through RNA editing. In common with other plant mitochondrial genes, there is a strong bias toward the use of U (36.3%) in the third position of codons, which probably means the tRNAs corresponding to these codons are more abundant than others. I also presented 251 by of 5-noncoding region and 107 by of 3´-noncoding region. There is a putative ribosomal binding site at -14 to -21 positions from the translation initiation colon which shows a 75% sequence identity to an octanucleotide sequence capable of binding to maize 18s rRNA. An extensive stem-loop structure resembling the transcription terminator structure is possible from 34 to 67 by downstream from the 3´ of the translation stop codon. There is also a long direct repeat of 29 by highly rich in AT (82%) which overlaps with the stem-loop structure. Nucleotide sequence comparison of the rice col with the maize cool revealed the sequence divergence is mainly due to insertions or deletions of stretches of nucleotides rather than point mutations. Based on detailed examination of other examples presented earlier from studies on co/ and co// genes, I strongly suggest that the significant divergence in sequence and size of the plant mitochondrial genomes is largely due to the deletion or addition mediated by the flanking direct repeats. To describe the processes involved in this dynamic nature of plant mitochondrial genomes, I propose two mechanisms: `slipped-mispairing during replication´ and `homologous recombination independent of replication´.
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