Centre for Medical Bioscience, School of Biological Sciences, University of Wollongong, Wollongong, NSW, Australia.
Mol Biol Evol. 2014 Mar;31(3):636-44. doi: 10.1093/molbev/mst255. Epub 2013 Dec 11.
Recombination has been proposed as a possible mechanism to explain mitochondrial (mt) gene rearrangements, although the issue of whether mtDNA recombination occurs in animals has been controversial. In this study, we sequenced the entire mt genome of the megaspilid wasp Conostigmus sp., which possessed a highly rearranged mt genome. The sequence of the A+T-rich region contained a number of different types of repeats, similar to those reported previously in the nematode Meloidogyne javanica, in which recombination was discovered. In Conostigmus, we detected the end products of recombination: a range of minicircles. However, using isolated (cloned) fragments of the A+T-rich region, we established that some of these minicircles were found to be polymerase chain reaction (PCR) artifacts. It appears that regions with repeats are prone to PCR template switching or PCR jumping. Nevertheless, there is strong evidence that one minicircle is real, as amplification primers that straddle the putative breakpoint junction produce a single strong amplicon from genomic DNA but not from the cloned A+T-rich region. The results provide support for the direct link between recombination and mt gene rearrangement. Furthermore, we developed a model of recombination which is important for our understanding of mtDNA evolution.
重组被认为是解释线粒体（mt）基因重排的一种可能机制，尽管关于动物中线粒体 DNA 重组是否发生的问题一直存在争议。在这项研究中，我们对拥有高度重排线粒体基因组的巨型黄蜂 Conostigmus sp. 的整个 mt 基因组进行了测序。富含 A+T 的区域的序列包含了多种不同类型的重复，与先前在发现重组的线虫 Meloidogyne javanica 中报告的重复相似。在 Conostigmus 中，我们检测到了重组的最终产物：一系列小型环。然而，使用富含 A+T 的区域的分离（克隆）片段，我们确定其中一些小型环是聚合酶链反应（PCR）的人为产物。似乎富含重复的区域容易发生 PCR 模板转换或 PCR 跳跃。尽管如此，有强有力的证据表明一个小型环是真实存在的，因为跨越假定断点连接的扩增引物可以从基因组 DNA 中产生单一强扩增子，但不能从克隆的富含 A+T 的区域中产生。这些结果为重组与 mt 基因重排之间的直接联系提供了支持。此外，我们提出了一种重组模型，这对于我们理解 mtDNA 进化很重要。
