Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7610001, Israel.
The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, Faculty of Agriculture, Hebrew University of Jerusalem, 229 Herzl St., Rehovot 7610001, Israel.
Mol Biol Evol. 2022 Sep 1;39(9). doi: 10.1093/molbev/msac178.
Fitness landscape mapping and the prediction of evolutionary trajectories on these landscapes are major tasks in evolutionary biology research. Evolutionary dynamics is tightly linked to the landscape topography, but this relation is not straightforward. Here, we analyze a fitness landscape of a yeast tRNA gene, previously measured under four different conditions. We find that the wild type allele is sub-optimal, and 8-10% of its variants are fitter. We rule out the possibilities that the wild type is fittest on average on these four conditions or located on a local fitness maximum. Notwithstanding, we cannot exclude the possibility that the wild type might be fittest in some of the many conditions in the complex ecology that yeast lives at. Instead, we find that the wild type is mutationally robust ("flat"), while more fit variants are typically mutationally fragile. Similar observations of mutational robustness or flatness have been so far made in very few cases, predominantly in viral genomes.
适应性景观测绘以及在这些景观上预测进化轨迹是进化生物学研究的主要任务。进化动态与景观地形紧密相关，但这种关系并不简单。在这里，我们分析了一个先前在四种不同条件下测量的酵母 tRNA 基因的适应性景观。我们发现野生型等位基因是次优的，其 8-10%的变体更适合。我们排除了野生型在这四种条件下平均是最适合的，或者位于局部适应最大值的可能性。然而，我们不能排除野生型在酵母生活的复杂生态系统中的许多条件下可能是最适合的可能性。相反，我们发现野生型是突变稳健的（“平坦的”），而更适合的变体通常是突变脆弱的。到目前为止，在极少数情况下观察到了类似的突变稳健性或平坦性，主要是在病毒基因组中。
