Lalić J, Elena S F
Instituto de Biología Molecular y Celular de Plantas, CSIC-UPV, València, Spain.
The Santa Fe Institute, Santa Fe, NM, USA.
J Evol Biol. 2015 Dec;28(12):2236-47. doi: 10.1111/jeb.12748. Epub 2015 Sep 22.
RNA viruses are the main source of emerging infectious diseases because of the evolutionary potential bestowed by their fast replication, large population sizes and high mutation and recombination rates. However, an equally important property, which is usually neglected, is the topography of the fitness landscape. How many fitness maxima exist and how well they are connected is especially interesting, as this determines the number of accessible evolutionary pathways. To address this question, we have reconstructed a region of the fitness landscape of tobacco etch potyvirus constituted by mutations observed during the experimental adaptation of the virus to the novel host Arabidopsis thaliana. Fitness was measured for many genotypes and showed the existence of multiple peaks and holes in the landscape. We found prevailing epistatic effects between mutations, with cases of reciprocal sign epistasis being common among pairs of mutations. We also found that high-order epistasis was as important as pairwise epistasis in their contribution to fitness. Therefore, results suggest that the landscape was rugged due to the existence of holes caused by lethal genotypes, that a very limited number of potential neutral paths exist and that it contained a single adaptive peak.
RNA病毒是新发传染病的主要来源，这是由于其快速复制、庞大的种群规模以及高突变和重组率赋予了它们进化潜力。然而，一个同样重要但通常被忽视的特性是适应度景观的地形。存在多少个适应度最大值以及它们之间的连通程度如何，这一点尤其有趣，因为这决定了可及的进化路径数量。为了解决这个问题，我们重建了烟草蚀纹马铃薯Y病毒适应度景观的一个区域，该区域由病毒在实验适应新宿主拟南芥过程中观察到的突变构成。对许多基因型的适应度进行了测量，结果表明该景观中存在多个峰值和空洞。我们发现突变之间普遍存在上位性效应，在成对突变中，互作符号上位性的情况很常见。我们还发现高阶上位性对适应度的贡献与成对上位性同样重要。因此，结果表明，由于致死基因型导致的空洞的存在，该景观崎岖不平，存在非常有限数量的潜在中性路径，并且它包含一个单一的适应性峰值。
