Department of Biology, Western University, London, Ontario, Canada.
PLoS One. 2013 Sep 5;8(9):e73325. doi: 10.1371/journal.pone.0073325. eCollection 2013.
When species interbreed, the hybrid offspring that are produced are often sterile. If only one hybrid sex is sterile, it is almost always the heterogametic (XY or ZW) sex. Taking this trend into account, the predominant model used to explain the genetic basis of F1 sterility involves a deleterious interaction between recessive sex-linked loci from one species and dominant autosomal loci from the other species. This model is difficult to evaluate, however, as only a handful of loci influencing interspecies hybrid sterility have been identified, and their autosomal genetic interactors have remained elusive. One hindrance to their identification has been the overwhelming effect of the sex chromosome in mapping studies, which could 'mask' the ability to accurately map autosomal factors. Here, we use a novel approach employing attached-X chromosomes to create reciprocal backcross interspecies hybrid males that have a non-recombinant sex chromosome and recombinant autosomes. The heritable variation in phenotype is thus solely caused by differences in the autosomes, thereby allowing us to accurately identify the number and location of autosomal sterility loci. In one direction of backcross, all males were sterile, indicating that sterility could be entirely induced by the sex chromosome complement in these males. In the other direction, we identified nine quantitative trait loci that account for a surprisingly large amount (56%) of the autosome-induced phenotypic variance in sterility, with a large contribution of autosome-autosome epistatic interactions. These loci are capable of acting dominantly, and thus could contribute to F1 hybrid sterility.
当物种杂交时，产生的杂种后代通常是不育的。如果只有一个杂种性别是不育的，那几乎总是异配子性别（XY 或 ZW）。考虑到这一趋势，用于解释 F1 不育遗传基础的主要模型涉及来自一个物种的隐性性连锁基因座与来自另一个物种的显性常染色体基因座之间的有害相互作用。然而，这个模型很难评估，因为只有少数几个影响种间杂种不育的基因座已经被确定，其常染色体遗传相互作用仍然难以捉摸。它们的鉴定存在一个障碍，即在图谱研究中性染色体的压倒性影响，这可能“掩盖”了准确图谱常染色体因素的能力。在这里，我们使用一种新颖的方法，利用附加的 X 染色体来创建具有非重组性染色体和重组常染色体的相互回交种间杂种雄性。表型的可遗传变异完全是由常染色体的差异引起的，从而使我们能够准确地识别常染色体不育基因座的数量和位置。在回交的一个方向上，所有雄性都是不育的，这表明在这些雄性中，不育完全可以由性染色体组成诱导。在另一个方向上，我们鉴定了九个数量性状基因座，它们解释了不育的常染色体诱导表型方差的惊人大部分（56%），其中常染色体-常染色体上位性相互作用的贡献很大。这些基因座能够表现出显性作用，因此可能导致 F1 杂种不育。
