Contribution of individual random mutations to genotype-by-environment interactions in Escherichia coli

Abstract

Numerous studies have shown genotype-by-environment (G؋E) interactions for traits related to organismal fitness. However, the genetic architecture of the interaction is usually unknown because these studies used genotypes that differ from one another by many unknown mutations. These mutations were also present as standing variation in populations and hence had been subject to prior selection. Based on such studies, it is therefore impossible to say what fraction of new, random mutations contributes to G؋E interactions. In this study, we measured the fitness in four environments of 26 genotypes of Escherichia coli, each containing a single random insertion mutation. Fitness was measured relative to their common progenitor, which had evolved on glucose at 37°C for the preceding 10,000 generations. The four assay environments differed in limiting resource and temperature (glucose, 28°C; maltose, 28°C; glucose, 37°C; and maltose, 37°C). A highly significant interaction between mutation and resource was found. In contrast, there was no interaction involving temperature. The resource interaction reflected much higher among mutation variation for fitness in maltose than in glucose. At least 11 mutations (42%) contributed to this G؋E interaction through their differential fitness effects across resources. Beneficial mutations are generally thought to be rare but, surprisingly, at least three mutations (12%) significantly improved fitness in maltose, a resource novel to the progenitor. More generally, our findings demonstrate that G؋E interactions can be quite common, even for genotypes that differ by only one mutation and in environments differing by only a single factor.GϫE interaction ͉ GEI ͉ phenotypic plasticity ͉ fitness ͉ evolution

Dietary stress does not strengthen selection against single deleterious mutations in Drosophila melanogaster

“…While this is supported for some alleles (for example, Korona, 1999;Remold and Lenski, 2001;Szafraniec et al, 2001;Fry and Heinsohn, 2002;Baer et al, 2006), for others there is little or no evidence for increased strength of selection with stress (Korona, 1999;Kishony and Leibler, 2003;Baer et al, 2006). The current study provides additional support for the view that stress does not, on average, increase the efficacy of selection.…”

Cost of Adaptation and Fitness Effects of Beneficial Mutations inPseudomonas fluorescens

“…It is notable that the magnitude of V GE is on the same order as that found using a small set of random insertion mutants in Escherichia coli (Remold and Lenski 2001) or in agronomic studies using a set of genotypes that are potentially a lot more divergent genetically (Bell 1997). We have at present no compelling explanation for this finding, except to say that this reinforces the conclusion that there is little that is distinctive about the top 18 mutants that were beneficial in LB.…”

“…Specifically, we are interested in the following four questions: (1) What are the effects of beneficial mutations on the degree of niche specialization? This question is one component of the larger issue concerning the extent to which single mutations contribute to G·E interaction (Remold and Lenski 2001). (2) How general is the prediction of an exponential DFE?…”

Mapping phenotypic plasticity and genotype–environment interactions affecting life-history traits in Caenorhabditis elegans

“…Similar results were obtained by Hausmann et al (2005), also for Arabidopsis. Following the work of Remold and Lenski (2001), although obtained for E. coli, we expect that these environment specific regions likely harbor many genes affecting GEI rather than a few single so-called 'plasticity' genes.…”