Molecular cytological studies on the mechanism of male mitochondria during maternal inheritance of mitochondria.

在多绒泡菌中，一半线粒体中DAPI染色的mtDNA荧光同时下降，出现小斑点，在核聚变后约1 h完全消失，而其他mt-类核和所有线粒体鞘保持不变。单个受精卵细胞的PCR分析证实，损失仅限于来自一个亲本的mtDNA。mtDNA被消化后，mt-核样蛋白也很快分散。分散的mt-核样蛋白从线粒体中被清除。交配后60 h，线粒体鞘逐渐消失。利用6种交配类型，研究了mtDNA在所有可能杂交中的传播模式。在60个杂交中有39个，严格的单代遗传被证实与相对性别等级一致。然而，在其他杂交中，双亲的mtDNA传递给了疟原虫。估计亲本mtDNA的比例为1:1 ~ 1:10^<-4>。尽管如此，还是遵循了matA的等级制度。在这些杂交中，mtDNA被不完全消化，mtDNA在随后的质体发育中复制。我们的结论是，mtDNA的快速、选择性消化促进了线粒体的单代遗传；当这种方法失败时，就会发生双亲代继承。我们使用原生PAGE和SDS-PAGE进行DNA酶谱分析，研究了年轻受精卵的DNA酶活性，发现了两种新的线粒体DNA酶活性，一种是50 kDa的Ca^<2+>-依赖性DNA酶，一种是13 kDa的Mn^<2+>-+依赖性DNA酶。我们认为，一些未知因素对线粒体核酸酶的调节是消化来自一方亲本的mtDNA的关键。

The fluorescence of mtDNA stained with DAPI in half of the mitochondria decreased simultaneously to give small spots, and then disappeared completely about 1 h after nuclear fusion, while the other mt-nucleoids and all of the mitochondrial sheaths remained unchanged in Physarum polycehalum. PCR analysis of single zygote cells confirmed that the loss was limited to mtDNA from one parent. The mt-nucleoid protein also dispersed soon after the digestion of mtDNA. The dispersed mt-nucleoid protein was eliminated from mitochondria. The vacant mitochondrial sheaths were gradually eliminated by 60 h after mating. Using six mating types, the transmission patterns of mtDNA were examined in all possible crosses. In 39 of 60 crosses, strict uniparental inheritance was confirmed in accordance with a hierarchy of relative sexuality. In the other crosses, however, mtDNA from both parents was transmitted to plasmodia. The ratio of parental mtDNA was estimated to be from 1:1 to 1:10^<-4>. Nevertheless, the matA hierarchy was followed. In these crosses, the mtDNA was incompletely digested, and mtDNA replicated during subsequent plasmodial development. We conclude that the rapid, selective digestion of mtDNA promotes the uniparental inheritance of mitochondria ; when this fails, biparental inheritance occurs. We used DNA zymography assays with native PAGE and SDS-PAGE to investigate the DNase activities in young zygotes, and identified two novel mitochondrial DNase activities a 50 kDa Ca^<2+>-dependent DNase, and a 13-kDa Mn^<2+>-+dependent DNase. We propose that the regulation of the mitochondrial nuclease by some unknown factor is the key to digestion of the mtDNA from one parent.