A genetic system controlling mitochondrial fusion in the slime mould, Physarum polycephalum.
A genetic system controlling mitochondrial fusion in the slime mould, Physarum polycephalum.
复制标题
控制粘菌多头绒泡菌线粒体融合的遗传系统。
作者：
S. Kawano;H. Takano;J. Imai;K. Mori;T. Kurioiwa
我们鉴定了两种不同的线粒体表型，即Mif+(线粒体融合)和Mif-(线粒体融合缺陷)，并研究了多头绒泡菌中控制线粒体融合的遗传系统。在所有Mif+疟原虫菌株中都鉴定出一个约16kbp的线粒体质粒。该质粒明显负责促进线粒体融合，并在与Mif-株连续有性杂交时插入线粒体DNA(MtDNA)。这种重组的mtDNA和未改变的游离质粒通过促进线粒体融合在线粒体群体中传播。携带该质粒的Mif+菌株进一步分为两种类型：高频线粒体融合和低频线粒体融合。对mtDNA的限制性内切酶分析表明，高频线粒体融合型更多地是异质性的；在每个原质团中，除了存在质粒外，通常还存在两种亲本类型的mtDNA。对来自三个不同分离物的粘阿米巴杂交后代的遗传分析表明，这些后代在控制线粒体融合频率的核基因座上携带不同的等位基因。这些等位基因(线粒体交配型等位基因mitA1、2和3)的功能似乎与粘阿米巴的交配型相似；线粒体融合与不同的等位基因组合发生的频率很高，但与相似等位基因的组合发生的频率较低。
We have identified two distinct mitochondrial phenotypes, namely, Mif+ (mitochondrial fusion) and Mif- (mitochondrial fusion-deficient), and have studied the genetic system that controls mitochondrial fusion in the slime mould, Physarum polycephalum. A mitochondrial plasmid of approximately 16 kbp was identified in all Mif+ plasmodial strains. This plasmid is apparently responsible for promoting mitochondrial fusion, and it is inserted into the mitochondrial DNA (mtDNA) in successive sexual crossing with Mif- strains. This recombinant mtDNA and the unchanged free plasmid spread through the mitochondrial population via the promotion of mitochondrial fusion. The Mif+ strains with the plasmid were further classified as being two types: high frequency and low frequency mitochondrial fusion. Restriction analysis of the mtDNA suggested that the high frequency mitochondrial fusion type was more often heteroplasmic; within each plasmodium, mtDNAs of both parental types were usually present, in addition to the presence of the plasmid. Genetic analysis with the progeny obtained from crossing myxamoebae derived from three different isolates suggested that these progeny carried different alleles at a nuclear locus that controlled the frequency of mitochondrial fusion. These alleles (mitochondrial mating-type alleles, mitA1, 2 and 3) appear to function like the mating type of the myxamoebae; mitochondrial fusion occurs at high frequency with the combination of unlike alleles, but at low frequency with the combination of like alleles.