Christie Joshua R, Schaerf Timothy M, Beekman Madeleine
School of Biological Sciences, The University of Sydney, Sydney, Australia; Centre for Mathematical Biology, The University of Sydney, Sydney, Australia.
PLoS Genet. 2015 Apr 16;11(4):e1005112. doi: 10.1371/journal.pgen.1005112. eCollection 2015 Apr.
Why are mitochondria almost always inherited from one parent during sexual reproduction? Current explanations for this evolutionary mystery include conflict avoidance between the nuclear and mitochondrial genomes, clearing of deleterious mutations, and optimization of mitochondrial-nuclear coadaptation. Mathematical models, however, fail to show that uniparental inheritance can replace biparental inheritance under any existing hypothesis. Recent empirical evidence indicates that mixing two different but normal mitochondrial haplotypes within a cell (heteroplasmy) can cause cell and organism dysfunction. Using a mathematical model, we test if selection against heteroplasmy can lead to the evolution of uniparental inheritance. When we assume selection against heteroplasmy and mutations are neither advantageous nor deleterious (neutral mutations), uniparental inheritance replaces biparental inheritance for all tested parameter values. When heteroplasmy involves mutations that are advantageous or deleterious (non-neutral mutations), uniparental inheritance can still replace biparental inheritance. We show that uniparental inheritance can evolve with or without pre-existing mating types. Finally, we show that selection against heteroplasmy can explain why some organisms deviate from strict uniparental inheritance. Thus, we suggest that selection against heteroplasmy explains the evolution of uniparental inheritance.
为什么在有性生殖过程中，线粒体几乎总是从双亲中的一方遗传而来？对于这个进化之谜，目前的解释包括避免核基因组与线粒体基因组之间的冲突、清除有害突变以及优化线粒体-核共同适应。然而，数学模型未能表明在任何现有假设下单亲遗传能够取代双亲遗传。最近的实验证据表明，在一个细胞内混合两种不同但正常的线粒体单倍型（异质性）会导致细胞和生物体功能异常。我们使用一个数学模型来测试针对异质性的选择是否会导致单亲遗传的进化。当我们假设针对异质性的选择且突变既无优势也无劣势（中性突变）时，对于所有测试的参数值，单亲遗传都会取代双亲遗传。当异质性涉及有利或有害的突变（非中性突变）时，单亲遗传仍然可以取代双亲遗传。我们表明，无论是否存在预先存在的交配类型，单亲遗传都可以进化。最后，我们表明针对异质性的选择可以解释为什么一些生物体偏离了严格的单亲遗传。因此，我们认为针对异质性的选择解释了单亲遗传的进化。
