Chiotti Kami E, Kvitek Daniel J, Schmidt Karen H, Koniges Gregory, Schwartz Katja, Donckels Elizabeth A, Rosenzweig Frank, Sherlock Gavin
Division of Biological Sciences, University of Montana, Missoula, MT, USA.
Department of Genetics, Stanford University, Stanford, CA 94305-5120, USA.
Genomics. 2014 Dec;104(6 Pt A):431-7. doi: 10.1016/j.ygeno.2014.10.011. Epub 2014 Nov 1.
The fitness landscape is a powerful metaphor for describing the relationship between genotype and phenotype for a population under selection. However, empirical data as to the topography of fitness landscapes are limited, owing to difficulties in measuring fitness for large numbers of genotypes under any condition. We previously reported a case of reciprocal sign epistasis (RSE), where two mutations individually increased yeast fitness in a glucose-limited environment, but reduced fitness when combined, suggesting the existence of two peaks on the fitness landscape. We sought to determine whether a ridge connected these peaks so that populations founded by one mutant could reach the peak created by the other, avoiding the low-fitness "Valley-of-Death" between them. Sequencing clones after 250 generations of further evolution provided no evidence for such a ridge, but did reveal many presumptive beneficial mutations, adding to a growing body of evidence that clonal interference pervades evolving microbial populations.
适应度景观是一种强大的隐喻，用于描述在选择作用下种群的基因型与表型之间的关系。然而，由于在任何条件下测量大量基因型的适应度都存在困难，关于适应度景观地形的实证数据有限。我们之前报道过一个相互符号上位性（RSE）的案例，其中两个突变在葡萄糖受限环境中单独增加了酵母的适应度，但组合在一起时却降低了适应度，这表明适应度景观上存在两个峰值。我们试图确定是否有一个山脊连接这些峰值，以便由一个突变体建立的种群能够到达由另一个突变体产生的峰值，避开它们之间低适应度的“死亡谷”。在进一步进化250代后对克隆进行测序，没有发现这种山脊存在的证据，但确实揭示了许多推测的有益突变，这进一步证明了克隆干扰在不断进化的微生物种群中普遍存在。
