Adaptive Mutation inSaccharomyces cerevisiae

Abstract

Adaptive mutation is a generic term for processes that allow individual cells of nonproliferating cell populations to acquire advantageous mutations and thereby to overcome the strong selective pressure of proliferation-limiting environmental conditions. Prerequisites for an occurrence of adaptive mutation are that the selective conditions are nonlethal and that a restart of proliferation may be accomplished by some genetic change in principle. The importance of adaptive mutation is derived from the assumption that it may, on the one hand, result in an accelerated evolution of microorganisms and, on the other, in multicellular organisms may contribute to a breakout of somatic cells from negative growth regulation, i.e., to cancerogenesis. Most information on adaptive mutation in eukaryotes has been gained with the budding yeast Saccharomyces cerevisiae. This review focuses comprehensively on adaptive mutation in this organism and summarizes our current understanding of this issue.

Inherited adaptation of genome‐rewired cells in response to a challenging environment

“…No doubt that the fraction of cells, which adapted on the plates, either in solid or in liquid medium experiments, was unprecedentedly high and, thus, stands in contrast to previous evolutionary experiments that found much lower rates (one in 10 5 -10 9 cells) at which adaptive phenotypes rose under stressful conditions (Paquin and Adams, 1983;Lenski and Travisano, 1994;Storchová et al, 1998;Elena and Lenski, 2003;Heidenreich, 2007). In previous studies adaptive phenotypes were observed in rates that matched the rates of genetic mutations and, indeed, in several such studies, mutations were found to be the causative agents of the new phenotypes.…”

“…However, up until now, in spite of major efforts to identify such and although some cases are still under debate, there is no conclusive evidence in the literature for the existence of adaptive mutations (Cairns et al, 1988;Cairns and Foster, 1991;Steele and Jinks-Robertson, 1992;Hall, 1998aHall, , 1998bRosenberg, 2001;Roth et al, 2006). Even if adaptive mutations were in consensus, in previous studies revertants in response to stressful conditions and induced adaptive mutations were reported to occur only in a minute fraction ͑ϳ10 −6 ͒ of the population (Storchová et al, 1998;Heidenreich, 2007) and not in 50% of the cells such as in our experiments. Other phenomena with some resemblance to what we described here were also studied.…”

The effect of sexual harassment on lethal mutation rate in femaleDrosophila melanogaster

“…The genome-wide mutation rate per individual and generation, U, is a key parameter in population genetics, which has been used extensively in many theoretical models in evolutionary biology [1][2][3][4]. The mutation rate has generally been assumed to be fixed across individuals within populations [5], although it has been speculated that an increased mutation rate could be an adaptive response of a genotype exposed to an unfavourable environment [6]. Nevertheless, several early studies hinted at the possibility that individual mutation rate can depend on the genotype or the physiological condition of the individual [7].…”

Genetic Adaptation of Phytoplankters to Herbicides

“…But after being further incubated a few cultures became green again, due to the growth of variants that were resistant to the herbicides. By using the fluctuation analysis, we demonstrated that resistance in different species of phytoplankters was due to the arising of new genetic variants caused by rare spontaneous mutation occurring randomly during propagation under non-selective conditions for the herbicides DCMU, glyphosate, simazine and diquat López-Rodas et al, 2001, 2007Marvá et al, 2010;see Table 1 shows the figures of mutation rate from herbicide-sensitivity to herbicide-resistance in different species of phytoplankters (ranging from 0.4 to 17.9 mutants per 10 6 cells per generation, depending of the species and the herbicide). Since mutation is recurrent in each generation, new mutant cells are arising continuously.…”

“…Under toxic but sub-lethal doses of herbicides, adaptation could be supported by modification of gene expression occurring in a short time (days to weeks) and within one organism's lifetime (i.e. physiological adaptation, also called acclimatization; Bradshaw & Hardwick, 1989); however, some evolutionary studies in bacteria (Cairns et al, 1988;Foster, 2000;Roth et al, 2006) and yeasts (Heidenreich, 2007) have suggested that adaptive mutations could be a process resembling Lamarckism which, in the absence of lethal selection, produces mutations that relieve selective pressure. Finally, under lethal doses of Marvá et al, 2010) herbicides, genetic adaptation supported by selection of new genetic variants originated by spontaneous mutation (Sniegowski & Lenski, 1995;Belfiore & Anderson 2001;Orr, 2005) is the only possibility.…”