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

多头绒泡菌线粒体DAPI染色的mtDNA荧光强度在核融合后1h左右完全消失，一半线粒体荧光减弱形成小斑点，其余线粒体核团和线粒体鞘基本不变。对单个受精卵细胞的聚合酶链式反应分析证实，这种缺失仅限于来自亲本的mtDNA。Mt-核蛋白在mtDNA消化后不久也分散了。线粒体中弥散分布的类核蛋白被清除。交配后60h，线粒体鞘逐渐消失。利用6种交配类型，对mtDNA在所有可能的杂交组合中的传播模式进行了检测。在60个杂交组合中的39个，严格的单亲遗传是根据相对性别的等级确定的。然而，在其他杂交组合中，来自双亲的mtDNA被传递给疟原虫。亲本mtDNA的比例为1：1~1：10。尽管如此，还是遵循了Mata等级制度。在这些杂交组合中，mtDNA没有被完全消化，mtDNA在随后的原生质体发育过程中复制。我们得出结论，线粒体DNA的快速、选择性消化促进了线粒体的单亲遗传；当这一过程失败时，就发生了双亲遗传。我们用DNA酶谱结合天然PAGE和SDS-PAGE对幼龄受精卵的DNase活性进行了研究，发现了两种新的线粒体DNase活性，一种是50 kDa Ca^&lt；2+&gt；依赖的DNase，另一种是13 kDa的Mn^&lt；2+&gt；-+依赖的DNase。我们认为一些未知因素对线粒体核酸酶的调节是从一个亲本中消化线粒体DNA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.