The fittest versus the flattest: experimental confirmation of the quasispecies effect with subviral pathogens.-猫眼课题宝

DOI：

10.1371/journal.ppat.0020136

发表时间：

2006-12

期刊：

PLoS pathogens

影响因子：

6.7

通讯作者：

中科院分区：

医学1区

文献类型：

作者：

Codoñer FM;Darós JA;Solé RV;Elena SF

来源链接：

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1757203/?report=classic

“适者生存”是达尔文进化论的范式，其中最适应的复制因子受到自然选择的青睐。然而，在高突变率下，最适合的生物体不一定是最快的复制者，而是那些对有害突变效应表现出最大鲁棒性的生物体，即使以低复制率为代价。这种情况被称为“最扁平的生存”，到目前为止只在数字生物体中出现过。我们表明，“最平坦的生存”也可以发生在生物实体通过分析两个类病毒物种共同感染同一植物之间的竞争的结果。在最佳的生长条件下，一个类病毒物种的特点是快速的人口增长和遗传同质性胜过一个类病毒物种与缓慢的人口增长和高度的变化。相比之下，当突变率增加时，生长缓慢的物种能够胜过生长快速的物种。这些实验结果得到了支持的竞争类病毒准种的计算机模型。达尔文的“适者生存”理论表明，速度较快的复制者能够战胜速度较慢的复制者。然而，当与基因组复制相关的突变被纳入图片时，情况变得有点复杂。在高突变率下，成为更快的复制者可能并不总是最好的选择;事实上，对突变的有害影响更具鲁棒性可能是更好的选择。如果在突变的稳定性和复制率之间存在一个折衷，例如，因为较快的聚合酶比较慢的聚合酶更容易出错，那么选择可能有利于生物体更快地复制或更稳定，但不能同时复制。在低突变率下，更快的复制因子将取代更健壮的复制因子。然而，超过临界突变率，较慢的复制因子应该会胜过较快的复制因子。这种现象被称为“最平者生存”。在这里，作者已经证实了这一预测，使用一对亚病毒植物病原体（类病毒）在正常和诱变条件下竞争。

The “survival of the fittest” is the paradigm of Darwinian evolution in which the best-adapted replicators are favored by natural selection. However, at high mutation rates, the fittest organisms are not necessarily the fastest replicators but rather are those that show the greatest robustness against deleterious mutational effects, even at the cost of a low replication rate. This scenario, dubbed the “survival of the flattest”, has so far only been shown to operate in digital organisms. We show that “survival of the flattest” can also occur in biological entities by analyzing the outcome of competition between two viroid species coinfecting the same plant. Under optimal growth conditions, a viroid species characterized by fast population growth and genetic homogeneity outcompeted a viroid species with slow population growth and a high degree of variation. In contrast, the slow-growth species was able to outcompete the fast species when the mutation rate was increased. These experimental results were supported by an in silico model of competing viroid quasispecies. Darwin's “survival of the fittest” suggests that faster replicators are able to outcompete slower ones. However, when mutation, unavoidably associated with genome replication, is incorporated into the picture, the situation becomes a bit more complicated. At a high mutation rate, being the faster replicator may not always be the best option; in fact, being the more robust against the pernicious effect of mutation may be a better option. If a tradeoff exists between mutational robustness and replication rate—for example, because faster polymerases are more prone to mistakes than slower ones—then selection may favor an organism to replicate faster or to be more robust, but not both at the same time. At a low mutation rate, a faster replicator would displace a robust one. However, beyond a critical mutation rate, the slower replicator should outcompete the faster replicator. This phenomenon is known as the “survival of the flattest”. Here, the authors have confirmed this prediction using a pair of subviral plant pathogens (viroids) competing under normal and mutagenic conditions.