Facultad de Ciencias Agrarias, IBAM, Universidad Nacional de Cuyo, CONICET, Almirante Brown 500, M5528AHB, Chacras de Coria, Argentina.
Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Cuyo, 5500, Mendoza, Argentina.
Plant Mol Biol. 2019 Jul;100(4-5):433-450. doi: 10.1007/s11103-019-00869-z. Epub 2019 Apr 9.
Cybrid plant mitochondria undergo homologous recombination, mainly BIR, keep a single allele for each gene, and maintain exclusive sequences of each parent and a single copy of the homologous regions. The maintenance of a dynamic equilibrium between the mitochondrial and nuclear genomes requires continuous communication and a high level of compatibility between them, so that alterations in one genetic compartment need adjustments in the other. The co-evolution of nuclear and mitochondrial genomes has been poorly studied, even though the consequences and effects of this interaction are highly relevant for human health, as well as for crop improvement programs and for genetic engineering. The mitochondria of plants represent an excellent system to understand the mechanisms of genomic rearrangements, chimeric gene formation, incompatibility between nucleus and cytoplasm, and horizontal gene transfer. We carried out detailed analyses of the mtDNA of a repeated cybrid between the solanaceae Nicotiana tabacum and Hyoscyamus niger. The mtDNA of the cybrid was intermediate between the size of the parental mtDNAs and the sum of them. Noticeably, most of the homologous sequences inherited from both parents were lost. In contrast, the majority of the sequences exclusive of a single parent were maintained. The mitochondrial gene content included a majority of N. tabacum derived genes, but also chimeric, two-parent derived, and H. niger-derived genes in a tobacco nuclear background. Any of these alterations in the gene content could be the cause of CMS in the cybrid. The parental mtDNAs interacted through 28 homologous recombination events and a single case of illegitimate recombination. Three main homologous recombination mechanisms were recognized in the cybrid mitochondria. Break induced replication (BIR) pathway was the most frequent. We propose that BIR could be one of the mechanisms responsible for the loss of the majority of the repeated regions derived from H. niger.
细胞杂种植物的线粒体经历同源重组，主要是 BIR，每个基因保持一个等位基因，并保持每个亲本的独特序列和同源区域的单个拷贝。线粒体和核基因组之间的动态平衡需要它们之间持续的沟通和高度的兼容性，以便一个遗传区室的改变需要在另一个遗传区室中进行调整。核和线粒体基因组的共同进化研究甚少，尽管这种相互作用的后果和影响对人类健康以及作物改良计划和基因工程都非常重要。植物的线粒体代表了一个极好的系统，可以了解基因组重排、嵌合基因形成、核质不相容性和水平基因转移的机制。我们对茄科烟草和天仙子之间的重复细胞杂种的 mtDNA 进行了详细分析。细胞杂种的 mtDNA 介于双亲 mtDNA 大小和它们的总和之间。值得注意的是，大多数从双亲遗传的同源序列丢失了。相比之下，大多数单一亲本特有的序列得到了维持。线粒体基因含量包括大多数烟草衍生的基因，但在烟草核背景中也有嵌合的、双亲衍生的和天仙子衍生的基因。基因含量中的任何这些改变都可能是细胞杂种 CMS 的原因。亲本 mtDNA 通过 28 个同源重组事件和一个单一的非合法重组事件相互作用。在细胞杂种线粒体中识别出三种主要的同源重组机制。断裂诱导复制 (BIR) 途径是最常见的。我们提出，BIR 可能是导致大多数来自天仙子的重复区域丢失的原因之一。
