Frequent Coinfection Reduces RNA Virus Population Genetic Diversity
Frequent Coinfection Reduces RNA Virus Population Genetic Diversity
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DOI：
10.1093/jhered/est038
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发表时间：
2013-09-01
影响因子：
3.1
通讯作者：
Turner, Paul E.
中科院分区：
文献类型：
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作者：
Dennehy, John J.;Duffy, Siobain;Turner, Paul E.
通过病毒片段的互补和重组（病毒性别）来掩盖有害突变，预计将增加共同感染病毒之间的群体遗传多样性。相反，克隆繁殖或非共感染的病毒群体可能会经历克隆干扰，其中病毒克隆相互竞争，阻止选择性扫描。这种动态降低了选择的效率，增加了遗传多样性。为了确定这些力量对群体遗传多样性的相对影响，我们进化了6个群体的噬菌体phi 6的条件下，促进或防止共同感染。经过300代，我们从每个群体中分离并部分测序了10个克隆。我们发现无性种群比有性种群的多样性更大。此外，有性种群没有表现出更大的相对适合度比无性种群，这意味着减少遗传变异并没有导致净化选择。然而，有性种群的遗传稳健性低于无性种群，可能更容易受到突变的有害上位效应的影响。因此，无性进化（健壮）背景上的中性突变可能对有性进化（脆弱）背景产生严重的危害。这可能有助于有性种群经历更大的净化选择以去除有害突变，但这种选择并没有反映在平均种群适应度的增加上。我们的研究结果支持了越来越多的文献，表明RNA病毒分割可能不是一种进化机制，因为它提供了性的普遍益处。
The masking of deleterious mutations by complementation and the reassortment of virus segments (virus sex) are expected to increase population genetic diversity among coinfecting viruses. Conversely, clonally reproducing or noncoinfecting virus populations may experience clonal interference where viral clones compete with one another, preventing selective sweeps. This dynamic reduces the efficiency of selection and increases the genetic diversity. To determine the relative influences of these forces on population genetic diversity, we evolved 6 populations of bacteriophage phi 6 under conditions promoting or preventing coinfection. Following 300 generations, we isolated and partially sequenced 10 clones from each population. We found greater diversity among asexual populations than sexual populations. Moreover, sexual populations did not show greater relative fitnesses than asexual populations, implying that reduced genetic variation did not result from purifying selection. However, sexual populations were less genetically robust than asexual populations and likely more prone to the deleterious epistatic effects of mutations. As such, a neutral mutation on the asexually evolved (robust) background could be profoundly deleterious on the sexually evolved (brittle) background. This could facilitate sexual populations undergoing greater purifying selection to remove deleterious mutations, but this selection is not reflected by increases in average population fitness. Our results bolster a growing literature suggesting that RNA virus segmentation is probably not a mechanism that evolved because it provides a generalized benefit of sex.