Epistasis Is a Major Determinant of the Additive Genetic Variance in Mimulus guttatus.
Epistasis Is a Major Determinant of the Additive Genetic Variance in Mimulus guttatus.
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DOI：
10.1371/journal.pgen.1005201
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发表时间：
2015-05
期刊：
影响因子：
4.5
通讯作者：
Kelly JK
中科院分区：
文献类型：
--
作者：
Monnahan PJ;Kelly JK
遗传互作（上位性）对数量性状遗传方差的影响是医学、农业和进化遗传学中尚未解决的主要问题。加性遗传成分通常在数量性状的总遗传方差中占很高的比例，尽管潜在的基因必须相互作用才能决定表型。本研究估计了影响花部性状的11对数量性状基因座（QTL）在单种群内的直接效应和互作效应。通过对每个QTL对的所有9种基因型的估计，我们能够将QTL效应映射到方差分量作为群体等位基因频率的函数，从而预测方差分量随等位基因频率变化的变化。这种映射需要一个分析框架，适当考虑到估计误差带来的偏差。我们发现，即使有大量的QTL之间的相互作用，大部分的遗传方差可能是加性的。然而，等位基因平均效应对遗传背景的强烈依赖性意味着上位性是加性遗传方差的主要决定因素，因此，人口的能力，以应对选择。复杂的性状不仅受到单个基因的影响，还受到这些基因相互作用的无数方式的影响，通常被称为上位性。理论表明，上位性可能有重要的人口水平的影响，在遗传变异的组成部分，控制进化的自然或人工选择。不幸的是，经验的例子，从观察到的基因之间的相互作用，遗传变异是很少的，特别是对自然种群。在这里，我们描述了M中自然分离多态性之间的上位性。并测定上位性对群体遗传方差分量的累积效应。要做到这一点，我们首先阐述必要的统计理论，以适应遗传效应的估计误差，因为不这样做将向上偏差方差预测。我们发现，基因的相互作用有一个净正效应的总遗传方差和加性遗传方差的大多数性状，然而，个别位点的贡献，加性方差在很大程度上取决于在其他位点的基因型频率。因此，上位性的影响超出了个体的表型，影响了群体及其组成等位基因对选择的反应。
The influence of genetic interactions (epistasis) on the genetic variance of quantitative traits is a major unresolved problem relevant to medical, agricultural, and evolutionary genetics. The additive genetic component is typically a high proportion of the total genetic variance in quantitative traits, despite that underlying genes must interact to determine phenotype. This study estimates direct and interaction effects for 11 pairs of Quantitative Trait Loci (QTLs) affecting floral traits within a single population of Mimulus guttatus. With estimates of all 9 genotypes for each QTL pair, we are able to map from QTL effects to variance components as a function of population allele frequencies, and thus predict changes in variance components as allele frequencies change. This mapping requires an analytical framework that properly accounts for bias introduced by estimation errors. We find that even with abundant interactions between QTLs, most of the genetic variance is likely to be additive. However, the strong dependency of allelic average effects on genetic background implies that epistasis is a major determinant of the additive genetic variance, and thus, the population’s ability to respond to selection. Complex traits are influenced not only by the effects of individual genes but also by the myriad ways that these genes interact with one another, commonly referred to as epistasis. Theory suggests that epistasis could have important population-level implications in terms of the genetic variance components that govern evolution in response to natural or artificial selection. Unfortunately, empirical examples extending from observed interactions between genes to genetic variances are scant, particularly for natural populations. Here, we characterize epistasis between naturally segregating polymorphisms in M. guttatus and determine the cumulative effect of epistasis on population genetic variance components. To do this, we first elaborate the necessary statistical theory to accommodate estimation error in genetic effects, as failing to do so will upwardly bias variance predictions. We find that gene interactions have a net positive effect on both the total and additive genetic variance for most traits; however, the contribution of individual loci to the additive variance depends heavily on the genotype frequencies at other loci. Therefore, the effect of epistasis extends beyond the individual’s phenotype to influence how both populations and their component alleles respond to selection.
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