Department of Biology and Biochemistry, University of Houston, Houston, TX 77204, USA.
Science. 2011 Jun 3;332(6034):1193-6. doi: 10.1126/science.1203801.
Epistatic interactions between mutations play a prominent role in evolutionary theories. Many studies have found that epistasis is widespread, but they have rarely considered beneficial mutations. We analyzed the effects of epistasis on fitness for the first five mutations to fix in an experimental population of Escherichia coli. Epistasis depended on the effects of the combined mutations--the larger the expected benefit, the more negative the epistatic effect. Epistasis thus tended to produce diminishing returns with genotype fitness, although interactions involving one particular mutation had the opposite effect. These data support models in which negative epistasis contributes to declining rates of adaptation over time. Sign epistasis was rare in this genome-wide study, in contrast to its prevalence in an earlier study of mutations in a single gene.
突变之间的上位性相互作用在进化理论中起着重要的作用。许多研究发现上位性是普遍存在的，但它们很少考虑有益突变。我们分析了在大肠杆菌实验种群中前五个固定突变的上位性对适应度的影响。上位性取决于组合突变的影响——预期收益越大，上位性效应越负。因此，上位性往往随着基因型适应度的增加而产生递减回报，尽管涉及特定突变的相互作用有相反的效果。这些数据支持了这样的模型，即负上位性有助于随着时间的推移适应率的下降。在这项全基因组研究中，正上位性很少见，而在之前对单个基因中突变的研究中则很常见。
