Woloszynska Magdalena, Kmiec Beata, Mackiewicz Pawel, Janska Hanna
Department of Cell Molecular Biology, Institute of Biochemistry and Molecular Biology, University of Wroclaw, Poland.
Plant Mol Biol. 2006 May;61(1-2):1-12. doi: 10.1007/s11103-005-5773-3.
Structural rearrangements characteristic for plant mitochondrial DNA often result in the appearance of genes in new genomic environments. The determination of the real number of gene copies is difficult since the in vivo structure of plant mitochondrial genomes is questionable. It is still uncertain whether the gene copy number regulates transcription in plant mitochondria. Using the real-time PCR technique we have quantified the copies of mitochondrial genes and their transcripts in four related Phaseolus vulgaris lines. We found low intergenomic variation both in the copy number of particular genes and the abundance of their transcripts, while the intragenomic differences between copy numbers and transcripts levels of various genes were much higher. Furthermore, we found that the appearance of a gene in a new location is not correlated with a proportional increase in its copy number estimated by real-time PCR. This observation seems to result from gene dosage compensation which is probably associated with the multimolecular plant mitochondrial genome structure and particularly with the recombinogenic activity of large repeats. Based on the relative gene copy numbers we propose the existence of two types of Phaseolus mitochondrial genomes: one associated with fertility and the other inducing cytoplasmic male sterility. We also show that there is no correlation between the observed number of copies of the analyzed genes and the steady-state level of their transcripts.
植物线粒体DNA特有的结构重排常常导致基因在新的基因组环境中出现。由于植物线粒体基因组的体内结构存在疑问，因此确定基因拷贝的实际数量很困难。基因拷贝数是否调节植物线粒体中的转录仍不确定。我们使用实时PCR技术对四个相关菜豆品系中线粒体基因及其转录本的拷贝数进行了定量。我们发现，特定基因的拷贝数及其转录本丰度在基因组间的差异较小，而不同基因的拷贝数和转录本水平在基因组内的差异要大得多。此外，我们发现一个基因出现在新位置与通过实时PCR估计的其拷贝数成比例增加无关。这一观察结果似乎源于基因剂量补偿，这可能与多分子植物线粒体基因组结构有关，特别是与大重复序列的重组活性有关。基于相对基因拷贝数，我们提出存在两种类型的菜豆线粒体基因组：一种与育性相关，另一种诱导细胞质雄性不育。我们还表明，所分析基因的观察到的拷贝数与其转录本的稳态水平之间没有相关性。
