School of Biological and Chemical Sciences, Queen Mary University of London, London, United Kingdom.
Genome Biol Evol. 2013;5(10):1969-77. doi: 10.1093/gbe/evt147.
Respiratory electron transport in mitochondria is coupled to ATP synthesis while generating mutagenic oxygen free radicals. Mitochondrial DNA mutation then accumulates with age, and may set a limit to the lifespan of individual, multicellular organisms. Why is this mutation not inherited? Here we demonstrate that female gametes-oocytes-have unusually small and simple mitochondria that are suppressed for DNA transcription, electron transport, and free radical production. By contrast, male gametes-sperm-and somatic cells of both sexes transcribe mitochondrial genes for respiratory electron carriers and produce oxygen free radicals. This germ-line division between mitochondria of sperm and egg is observed in both the vinegar fruitfly and the zebrafish-species spanning a major evolutionary divide within the animal kingdom. We interpret these findings as an evidence that oocyte mitochondria serve primarily as genetic templates, giving rise, irreversibly and in each new generation, to the familiar energy-transducing mitochondria of somatic cells and male gametes. Suppressed mitochondrial metabolism in the female germ line may therefore constitute a mechanism for increasing the fidelity of mitochondrial DNA inheritance.
线粒体中的呼吸电子传递与 ATP 合成耦联，同时产生诱变的氧自由基。线粒体 DNA 突变随着年龄的增长而积累，可能会对个体多细胞生物的寿命设定一个限制。为什么这种突变不会遗传？在这里，我们证明了雌性配子——卵母细胞——具有异常小而简单的线粒体，这些线粒体被抑制了 DNA 转录、电子传递和自由基产生。相比之下，雄性配子——精子——和两性的体细胞转录呼吸电子载体的线粒体基因并产生氧自由基。这种在精子和卵子线粒体之间的种系分裂在醋果蝇和斑马鱼中都有观察到，跨越了动物王国的主要进化分支。我们将这些发现解释为证据，表明卵母细胞线粒体主要作为遗传模板，不可逆地并在每一个新的世代中，产生体细胞和雄性配子中熟悉的能量转换线粒体。因此，雌性生殖系中被抑制的线粒体代谢可能构成了增加线粒体 DNA 遗传保真度的机制。
