School of Biological Sciences, University of Nebraska-Lincoln, 1104 T Street, Lincoln, NE 68502, USA.
Integr Comp Biol. 2019 Oct 1;59(4):890-899. doi: 10.1093/icb/icz091.
Strict maternal transmission of mitochondrial DNA (mtDNA) is hypothesized to permit the accumulation of mitochondrial variants that are deleterious to males but not females, a phenomenon called mother's curse. However, direct evidence that mtDNA mutations exhibit such sexually antagonistic fitness effects is sparse. Male-specific mutational effects can occur when the physiological requirements of the mitochondria differ between the sexes. Such male-specific effects could potentially occur if sex-specific cell types or tissues have energy requirements that are differentially impacted by mutations affecting energy metabolism. Here we summarize findings from a model mitochondrial-nuclear incompatibility in the fruit fly Drosophila that demonstrates sex-biased effects, but with deleterious effects that are generally larger in females. We present new results showing that the mitochondrial-nuclear incompatibility does negatively affect male fertility, but only when males are developed at high temperatures. The temperature-dependent male sterility can be partially rescued by diet, suggesting an energetic basis. Finally, we discuss fruitful paths forward in understanding the physiological scope for sex-specific effects of mitochondrial mutations in the context of the recent discovery that many aspects of metabolism are sexually dimorphic and downstream of sex-determination pathways in Drosophila. A key parameter of these models that remains to be quantified is the fraction of mitochondrial mutations with truly male-limited fitness effects across extrinsic and intrinsic environments. Given the energy demands of reproduction in females, only a small fraction of the mitochondrial mutational spectrum may have the potential to contribute to mother's curse in natural populations.
线粒体 DNA（mtDNA）的严格母体传递假设允许积累对男性有害但对女性无害的线粒体变异，这种现象称为“母亲的诅咒”。然而，直接证据表明 mtDNA 突变表现出这种性拮抗适应性效应是很少的。当线粒体的生理需求在两性之间存在差异时，就会发生雄性特异性突变效应。如果特定于性别的细胞类型或组织具有受影响能量代谢的突变影响的不同能量需求，则可能会发生这种雄性特异性效应。在这里，我们总结了在果蝇中发现的一种模型线粒体-核不兼容的研究结果，该研究表明存在性别偏向效应，但有害效应通常在雌性中更大。我们提出了新的结果，表明线粒体-核不兼容确实会降低雄性的生育能力，但只有在高温下雄性发育时才会发生这种情况。饮食可以部分挽救温度依赖性雄性不育，这表明存在能量基础。最后，我们讨论了在理解线粒体突变在果蝇性别决定途径下游的代谢许多方面具有性别二态性的背景下，线粒体突变的生理作用具有性别特异性的有前途的途径。这些模型中仍然需要量化的一个关键参数是，在外部和内部环境中，具有真正雄性局限性适应性效应的线粒体突变的比例。考虑到雌性繁殖的能量需求，只有一小部分线粒体突变谱有可能对自然种群中的“母亲的诅咒”做出贡献。
