Environmental stresses can alleviate the average deleterious effect of mutations.
Environmental stresses can alleviate the average deleterious effect of mutations.
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DOI：
10.1186/1475-4924-2-14
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发表时间：
2003
影响因子：
--
通讯作者：
Leibler S
中科院分区：
文献类型：
--
作者：
Kishony R;Leibler S
进化遗传学中的基本问题，包括有性生殖的可能优势，关键取决于有害突变对适应性的影响。有限的现有实验证据表明，平均而言，这种影响往往在环境压力下加剧，这与压力降低生物体耐受有害突变的能力的看法一致。在这里，我们问是否也有压力与相反的影响，在这种情况下，生物体变得更宽容的突变。我们开发了一种基于生物发光的技术，该技术允许在非常低的细胞密度下精确地自动测量细菌生长速率。使用这个系统，我们测量了大肠杆菌突变体的生长速率下的一组不同的环境压力。与压力总是降低生物体耐受突变的能力的观点相反，我们的测量确定了相反的压力-也就是说，尽管野生型生长减少，但平均而言，它们减轻了有害突变的影响。我们的结果显示了各种环境压力之间的质的差异，从突变平均效应的减轻到加剧。我们进一步展示了如何存在的压力，偏向于减轻突变的影响可能意味着平均上位突变之间的相互作用的存在。因此，这些结果提供了控制有害突变影响的两个主要因素之间的联系：环境条件和上位性相互作用。
Fundamental questions in evolutionary genetics, including the possible advantage of sexual reproduction, depend critically on the effects of deleterious mutations on fitness. Limited existing experimental evidence suggests that, on average, such effects tend to be aggravated under environmental stresses, consistent with the perception that stress diminishes the organism's ability to tolerate deleterious mutations. Here, we ask whether there are also stresses with the opposite influence, under which the organism becomes more tolerant to mutations. We developed a technique, based on bioluminescence, which allows accurate automated measurements of bacterial growth rates at very low cell densities. Using this system, we measured growth rates of Escherichia coli mutants under a diverse set of environmental stresses. In contrast to the perception that stress always reduces the organism's ability to tolerate mutations, our measurements identified stresses that do the opposite – that is, despite decreasing wild-type growth, they alleviate, on average, the effect of deleterious mutations. Our results show a qualitative difference between various environmental stresses ranging from alleviation to aggravation of the average effect of mutations. We further show how the existence of stresses that are biased towards alleviation of the effects of mutations may imply the existence of average epistatic interactions between mutations. The results thus offer a connection between the two main factors controlling the effects of deleterious mutations: environmental conditions and epistatic interactions.