Mitochondrial genomes in flowering plants differ from those in animals and yeasts in several ways, including having large and variable sizes, circular, linear and branched structures, long repeat sequences that participate in homologous recombinations, and variable genes orders, even within a species. Understanding these differences has been hampered by a lack of genetic methods for transforming plant mitochondrial genomes. We recently succeeded in disrupting targeted genes in mitochondrial genomes by mitochondria-targeted transcription activator-like effector nucleases (mitoTALENs) in rice, rapeseed, and Arabidopsis. Double-strand breaks created by mitoTALENs were repaired not by non-homologous end-joining (NHEJ) but by homologous recombination (HR) between repeats near and far from the target sites, resulting in new genomic structures with large deletions and different configurations. On the other hand, in mammals, TALENs-induced DSBs cause small insertions or deletions in nuclear genomes and degradation of mitochondrial genomes. These results suggest that the mitochondrial and nuclear genomes of plants and mammals have distinct mechanisms for responding to naturally occurring DSBs. The different responses appear to be well suited to differences in size and copy numbers of each genome.

中文翻译：

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线粒体定向双链断裂对植物线粒体基因组的影响

开花植物中的线粒体基因组与动物和酵母中的线粒体基因组在几个方面有所不同，包括具有较大且可变的大小，圆形，线性和分支的结构，参与同源重组的长重复序列以及可变的基因顺序，甚至在一个物种内。缺乏用于转化植物线粒体基因组的遗传方法阻碍了对这些差异的理解。我们最近成功地通过水稻，油菜籽和拟南芥中线粒体靶向的转录激活因子样效应子核酸酶（mitoTALENs）破坏了线粒体基因组中的靶向基因。。由mitoTALENs产生的双链断裂不是通过非同源末端连接（NHEJ）而是通过在靶位点附近和远离靶点的重复序列之间的同源重组（HR）修复的，从而导致了新的具有大缺失和不同构型的基因组结构。另一方面，在哺乳动物中，TALENs诱导的DSB导致核基因组中的少量插入或缺失以及线粒体基因组的降解。这些结果表明，植物和哺乳动物的线粒体和核基因组具有不同的机制来响应天然存在的DSB。不同的反应似乎非常适合每个基因组的大小和拷贝数的差异。