Genetic load may increase or decrease with selfing depending upon the recombination environment
Genetic load may increase or decrease with selfing depending upon the recombination environment
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DOI：
10.1101/2021.05.20.445016
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发表时间：
2021-05
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影响因子：
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通讯作者：
Shelley A. Sianta;Stephan Peischl;D. A. Moeller;Yaniv J Brandvain
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作者：
Shelley A. Sianta;Stephan Peischl;D. A. Moeller;Yaniv J Brandvain
理论预测，自然选择从种群中移除有害突变并防止遗传负荷积累的能力是有效种群大小(Ne)的函数。从随机交配到自交(“自交”)的转变预计会通过各种基因组变化来降低Ne--包括减少有效重组和增加纯合性。虽然长期的理论表明，选择的效率，特别是对非隐性突变的效率，应该随着自交率的下降而下降，但基于基因组的估计在相关的异交-自交对之间的选择效率的比较已经发现了相互矛盾的结果。我们通过模拟一系列重组、突变和选择性参数组合中强有害的隐性突变和弱有害的相加突变的演化来解决这一悖论。我们发现，种群的遗传负荷可以增加、减少或不随自交率而变化。只有当重组率大于突变率时，自体的遗传负荷才会更高。当重组率低于突变率时，隐性突变的积累会在异交群体中导致伪超显性，这是一种平衡选择。利用模拟和分析理论，我们证明了伪超显性对连锁加性突变的选择效率有很强的负面影响，并且阈值水平的自交可以防止伪超显性。我们的结果表明，根据有害突变率和基因密度之间的关系，自交者的选择可能或多或少地比异交者有效，因此不同类群中的不同基因组区域可能会显示不同的结果。
Theory predicts that the ability for natural selection to remove deleterious mutations from a population, and prevent the accumulation of genetic load, is a function of the effective population size (Ne). Shifts from random mating to self-fertilization (“selfing”) are predicted to decrease Ne through a variety of genomic changes - including a reduction in effective recombination and an increase in homozygosity. While a long history of theory suggests that the efficacy of selection, particularly against non-recessive mutations, should decrease with selfing rate, comparisons of genomic-based estimates of the efficacy of selection between related outcrosser-selfer pairs have revealed conflicting results. We address this paradox by simulating the evolution of strongly deleterious recessive and weakly deleterious additive mutations across a range of recombination, mutation and selective parameter combinations. We find that the genetic load of a population can either increase, decrease, or not vary with selfing rate. Genetic load is higher in selfers only when recombination rates are greater than mutation rates. When recombination rates are lower than mutation rates, an accumulation of recessive mutations leads to pseudo-overdominance, a type of balancing selection, in outcrossing populations. Using both simulations and analytical theory, we show that pseudo-overdominance has strong negative effects on the efficacy of selection against linked additive mutations and that a threshold level of selfing prevents pseudo-overdominance. Our results show that selection can be more or less effective in selfers as compared to outcrossers depending on the relationship between the deleterious mutation rate and gene density, and therefore different genomic regions in different taxa could show differing results.