Evolvability of an RNA virus is determined by its mutational neighbourhood
Evolvability of an RNA virus is determined by its mutational neighbourhood
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DOI：
10.1038/35020564
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发表时间：
2000-08-10
期刊：
影响因子：
64.8
通讯作者：
Chao, L
中科院分区：
文献类型：
--
作者：
Burch, CL;Chao, L
产生遗传变异的机制无处不在，这引发了一种争论，即进化性，即产生适应性变异的能力，本身就是对自然选择的反应。RNA病毒的高突变率被认为是对进化能力的适应，但矛盾的是，尽管一些RNA病毒以高速率进化，但另一些RNA病毒是高度稳定的。在这里，我们表明，RNA噬菌体φ6的进化性也取决于突变邻域（距离突变一步或几步的突变体集）内有利基因型的可及性。我们发现，来自同一个祖先噬菌体的两个φ6种群以不同的速率重复进化，并朝着不同的适应度最大值进化。个体适应度的测量表明，两个群体之间的突变体的适应度分布不同。种群A向较高的最大值进化，其分布含有许多有利的突变体，而种群B向较低的最大值进化，其分布只含有有害的突变体。我们解释这些分布，以衡量健身效果的基因型突变提供给两个人口。因此，φ6的可进化性受到其突变邻居的分布的限制，尽管该噬菌体具有RNA病毒特有的高突变率。
The ubiquity of mechanisms that generate genetic variation has spurred arguments that evolvability, the ability to generate adaptive variation, has itself evolved in response to natural selection,. The high mutation rate of RNA viruses is postulated to be an adaptation for evolvability,, but the paradox is that whereas some RNA viruses evolve at high rates,, others are highly stable,. Here we show that evolvability in the RNA bacteriophage φ6 is also determined by the accessibility of advantageous genotypes within the mutational neighbourhood (the set of mutants one or a few mutational steps away). We found that two φ6 populations that were derived from a single ancestral phage repeatedly evolved at different rates and toward different fitness maxima. Fitness measurements of individual phages showed that the fitness distribution of mutants differed between the two populations. Whereas population A, which evolved toward a higher maximum, had a distribution that contained many advantageous mutants, population B, which evolved toward a lower maximum, had a distribution that contained only deleterious mutants. We interpret these distributions to measure the fitness effects of genotypes that are mutationally available to the two populations. Thus, the /evolvability of φ6 is constrained by the distribution of its mutational neighbours, despite the fact that this phage has the characteristic high mutation rate of RNA viruses.