Wolf J B
Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
Evolution. 2000 Dec;54(6):1882-98. doi: 10.1111/j.0014-3820.2000.tb01235.x.
Theoretical analyses have demonstrated a potential role for epistasis in many of the most important processes in evolution. These analyses generally assume that an individual's genes map directly to its phenotype and epistasis results from interactions among loci that contribute to the same biochemical or developmental pathways (termed physiological, or within-genotype, epistasis). For many characters, particularly those expressed early in life, an individual's phenotype may also be affected by genes expressed by its parents. The presence of these parental effects allows for interactions between the genes present in the parental and offspring genomes. When the phenotypic effect of a locus in the offspring depends on the alleles possessed by its parents, genotype-by-genotype, or among-genotype, epistasis occurs. The among-genotype epistasis resulting from parental effects may contribute to ruggedness of adaptive landscapes because early mortality often accounts for much of the variance in fitness in populations. To demonstrate how parent-offspring interactions can result in among-genotype epistasis, I use a two-locus model, with one maternal effect locus and one direct effect locus, each with two alleles. Dynamical equations are presented for the two-locus model and are directly contrasted with the dynamical equations derived for a model for physiological epistasis. The relationship between the evolutionary dynamics resulting from these two forms of epistasis is discussed. Three scenarios are presented to illustrate systems in which maternal-offspring, genotype-by-genotype epistasis may occur. The implications of maternal-offspring epistasis for quantitative-trait-loci studies are also discussed.
理论分析表明，上位性在进化中许多最重要的过程中具有潜在作用。这些分析通常假定个体的基因直接映射到其表型，而上位性源于对相同生化或发育途径有贡献的基因座之间的相互作用（称为生理上位性或基因型内上位性）。对于许多性状，尤其是那些在生命早期表达的性状，个体的表型也可能受到其父母所表达基因的影响。这些亲代效应的存在使得亲代和子代基因组中存在的基因之间能够相互作用。当子代中一个基因座的表型效应取决于其父母所拥有的等位基因时，就会发生基因型对基因型或基因型间上位性。由亲代效应导致的基因型间上位性可能有助于适应度景观的崎岖性，因为早期死亡率往往占种群适应度方差的很大一部分。为了说明亲子代相互作用如何导致基因型间上位性，我使用了一个双基因座模型，其中一个是母本效应基因座，一个是直接效应基因座，每个基因座都有两个等位基因。给出了双基因座模型的动力学方程，并将其与为生理上位性模型推导的动力学方程直接进行对比。讨论了这两种上位性形式所产生的进化动力学之间的关系。提出了三种情况来说明可能发生母本-子代基因型对基因型上位性的系统。还讨论了母本-子代上位性对数量性状基因座研究的影响。
