Darwinian evolution preferentially follows mutational pathways whose individual steps increase fitness. Alternative pathways with mutational steps that do not increase fitness are less accessible. Here, we show that mistranslation, the erroneous incorporation of amino acids into nascent proteins, can increase the accessibility of such alternative pathways and, ultimately, of high fitness genotypes. We subject populations of the beta-lactamase TEM-1 to directed evolution in Escherichia coli under both low- and high-mistranslation rates, selecting for high activity on the antibiotic cefotaxime. Under low mistranslation rates, different evolving TEM-1 populations ascend the same high cefotaxime-resistance peak, which requires three canonical DNA mutations. In contrast, under high mistranslation rates they ascend three different high cefotaxime-resistance genotypes, which leads to higher genotypic diversity among populations. We experimentally reconstruct the adaptive DNA mutations and the potential evolutionary paths to these high cefotaxime-resistance genotypes. This reconstruction shows that some of the DNA mutations do not change fitness under low mistranslation, but cause a significant increase in fitness under high-mistranslation, which helps increase the accessibility of different high cefotaxime-resistance genotypes. In addition, these mutations form a network of pairwise epistatic interactions that leads to mutually exclusive evolutionary trajectories towards different high cefotaxime-resistance genotypes. Our observations demonstrate that protein mistranslation and the phenotypic mutations it causes can alter the evolutionary exploration of fitness landscapes and reduce the predictability of evolution.

中文翻译：

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误译可以促进对酶进化中替代进化轨迹的探索。

达尔文进化优先遵循突变途径，其个体步骤增加了适应度。具有不增加适应性的突变步骤的替代途径不太容易获得。在这里，我们表明错误翻译，即错误地将氨基酸掺入新生蛋白质中，可以增加此类替代途径的可及性，并最终增加高适应性基因型的可及性。我们将 β-内酰胺酶 TEM-1 群体置于低误译率和高误译率下的大肠杆菌中进行定向进化，选择抗生素头孢噻肟的高活性。在低误译率下，不同的进化 TEM-1 种群上升到相同的高头孢噻肟抗性峰，这需要三个典型的 DNA 突变。相比之下，在高误译率下，它们提升了三种不同的高头孢噻肟抗性基因型，这导致种群间基因型的多样性更高。我们通过实验重建了适应性 DNA 突变和这些头孢噻肟高抗性基因型的潜在进化路径。这种重建表明，一些 DNA 突变在低误译下不会改变适应度，但在高误译下导致适应度显着增加，这有助于增加不同高头孢噻肟基因型的可及性。此外，这些突变形成了一个成对的上位相互作用网络，导致朝向不同的头孢噻肟高抗性基因型的相互排斥的进化轨迹。