Kawano S, Nishibayashi S, Shiraishi N, Miyahara M, Kuroiwa T
Exp Cell Res. 1983 Dec;149(2):359-73. doi: 10.1016/0014-4827(83)90349-x.
In Physarum polycephalum, microplasmodia differentiated into spherules when cultures were aged for 8-10 days. Respiration rates of the microplasmodia decreased rapidly with ageing to a 90% decrease in oxygen consumption over 9 days. We studied this phenomena by isolating and characterizing mitochondria from microplasmodia and spherules at different stages of spherulation. Oxygen uptake by the isolated mitochondria decreased with spherulation. Morphological and biochemical analyses showed that mitochondrial differentiation to inactive state was characterized by a decrease not only in dimension but also of content (DNA, RNA and protein). Diminutive mitochondria contained small particle-shaped mitochondrial nuclei. The DNA content, measured by microscopic fluorometry, was about 1.15 and 0.58 X 10(-10) g, which corresponded to about 16 and 8 genome copies, respectively (e.g., 32 genome copies per mitochondrion at mitochondrial G1). Restriction endonuclease analysis showed that the physical structure and methylation pattern of the mtDNA had not changed although the DNA content per mitochondrion had decreased remarkably with spherulation. This showed that changes in the ploidy level of the mitochondrial nucleus during spherulation were due to reduction in the number of whole mitochondrial genomes.
在多头绒泡菌中，当培养8 - 10天时，微原质团会分化成小球体。随着培养时间的延长，微原质团的呼吸速率迅速下降，在9天内氧气消耗量减少了90%。我们通过分离和鉴定处于不同小球体化阶段的微原质团和小球体中的线粒体来研究这一现象。分离出的线粒体的氧气摄取量随着小球体化而降低。形态学和生化分析表明，线粒体向无活性状态的分化不仅表现为尺寸减小，还表现为含量（DNA、RNA和蛋白质）减少。微小的线粒体含有小颗粒状的线粒体核。通过显微荧光测定法测得的DNA含量分别约为1.15×10⁻¹⁰克和0.58×10⁻¹⁰克，分别对应约16个和8个基因组拷贝（例如，线粒体G1期每个线粒体有32个基因组拷贝）。限制性内切酶分析表明，尽管随着小球体化每个线粒体的DNA含量显著降低，但线粒体DNA的物理结构和甲基化模式并未改变。这表明在小球体化过程中线粒体核的倍性水平变化是由于整个线粒体基因组数量的减少。
