The Genetic Signature of Conditional Expression
The Genetic Signature of Conditional Expression
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DOI：
10.1534/genetics.109.110163
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发表时间：
2010-02-01
期刊：
影响因子：
3.3
通讯作者：
Wade, Michael J.
中科院分区：
文献类型：
--
作者：
Van Dyken, J. David;Wade, Michael J.
连续表达的基因具有这样的特性，即群体中的每个个体都携带并传递该基因，但只有一小部分（phi）表达该基因并使其暴露于自然选择。我们表明，这种遗传和表达模式的后果是削弱了自然选择的力量，允许有害突变在物种内和物种之间积累，并抑制有益突变的传播。我们扩展了以前的理论表明，在空间和时间的条件表达式有近似相等的效果放松选择的强度和效果保持在空间异质性的环境中，即使在补丁之间的迁移率低。我们支持我们的分析近似与计算机模拟，并描绘下的近似失败的参数范围。我们模拟了条件表达对突变-选择-漂移平衡下序列多态性的影响，允许中性位点，并表明条件表达使物种内和物种间的序列变异膨胀，在有效大小较大的群体中效果最强。随着phi降低，更多的位点被招募到中性，导致假基因化和增加的漂移负荷。突变积累减少了适应的程度条件表达的基因罕见的环境，和突变的表型可塑性，我们量化的可塑性负荷的成本，是更罕见的表达基因。我们的理论将基因水平的相对多态性和趋异与诱导基因表达的环境的时空频率联系起来。我们的理论表明，零假设水平的常设遗传变异和序列的分歧必须加以纠正，以占研究中的基因的表达频率。
Conditionally expressed genes have the property that every individual in a population carries and transmits the gene, but only a fraction, phi, expresses the gene and exposes it to natural selection. We show that a consequence of this pattern of inheritance and expression is a weakening of the strength of natural selection, allowing deleterious mutations to accumulate within and between species and inhibiting the spread of beneficial mutations. We extend previous theory to show that conditional expression in space and time have approximately equivalent effects on relaxing the strength of selection and that the effect holds in a spatially heterogeneous environment even with low migration rates among patches. We support our analytical approximations with computer simulations and delineate the parameter range under which the approximations fail. We model the effects of conditional expression on sequence polymorphism at mutation-selection-drift equilibrium, allowing for neutral sites, and show that sequence variation within and between species is inflated by conditional expression, with the effect being strongest in populations with large effective size. As phi decreases, more sites are recruited into neutrality, leading to pseudogenization and increased drift load. Mutation accumulation diminishes the degree of adaptation of conditionally expressed genes to rare environments, and the mutational cost of phenotypic plasticity, which we quantify as the plasticity load, is greater for more rarely expressed genes. Our theory connects gene-level relative polymorphism and divergence with the spatial and temporal frequency of environments inducing gene expression. Our theory suggests that null hypotheses for levels of standing genetic variation and sequence divergence must be corrected to account for the frequency of expression of the genes under study.