Rankin C T, Cutright M T, Makaroff C A
Chemistry Department, Hughes Hall, Miami University, Oxford, OH 45056, USA.
Curr Genet. 1996 May;29(6):564-71. doi: 10.1007/BF02426961.
In order to further investigate sequences that are responsible for low-frequency recombination in plant mitochondrial DNAs and RNA editing in radish mitochondria, the nad3/rps12 locus has been isolated and characterized from a normal cultivar of radish and the male-sterile Ogura cytoplasm. A repeated sequence that has been implicated in other radish mitochondrial DNA rearrangements was identified at the breakpoint between the two loci indicating that it was also involved in the nad3/rps12 rearrangement. Similar to some other radish mitochondrial genes, nad3/rps12 genomic sequences already contain several, but not all, of the bases that are typically edited in plant mitochondrial nad3 and rps12 genes. Analysis of nad3/rps12 cDNAs indicated that the mRNAs are not edited. One partially edited transcript was identified out of the twenty two that were examined. This finding, along with the observation that nad3/rps12 RNAs are present at very low levels, raises the possibility that radish mitochondria may not encode functional copies of these genes. Consistent with this hypothesis, DNA-blot analysis detects nad3/rps12 sequences in the nucleus.
为了进一步研究植物线粒体DNA中负责低频重组的序列以及萝卜线粒体中的RNA编辑，已从萝卜的一个正常品种和雄性不育的小仓细胞质中分离并鉴定了nad3/rps12基因座。在两个基因座之间的断点处鉴定出一个与其他萝卜线粒体DNA重排有关的重复序列，这表明它也参与了nad3/rps12重排。与其他一些萝卜线粒体基因类似，nad3/rps12基因组序列已经包含了植物线粒体nad3和rps12基因中通常被编辑的几个但不是全部碱基。对nad3/rps12 cDNA的分析表明，这些mRNA没有被编辑。在检测的22个转录本中，鉴定出一个部分编辑的转录本。这一发现，连同nad3/rps12 RNA水平非常低的观察结果，增加了萝卜线粒体可能不编码这些基因功能拷贝的可能性。与这一假设一致，DNA印迹分析在细胞核中检测到了nad3/rps12序列。
