Whole-Genome Effects of Ethyl Methanesulfonate-Induced Mutation on Nine Quantitative Traits in Outbred Drosophila melanogaster

Abstract

We induced mutations in Drosophila melanogaster males by treating them with 21.2 mm ethyl methanesulfonate (EMS). Nine quantitative traits (developmental time, viability, fecundity, longevity, metabolic rate, motility, body weight, and abdominal and sternopleural bristle numbers) were measured in outbred heterozygous F3 (viability) or F2 (all other traits) offspring from the treated males. The mean values of the first four traits, which are all directly related to the life history, were substantially affected by EMS mutagenesis: the developmental time increased while viability, fecundity, and longevity declined. In contrast, the mean values of the other five traits were not significantly affected. Rates of recessive X-linked lethals and of recessive mutations at several loci affecting eye color imply that our EMS treatment was equivalent to ∼100 generations of spontaneous mutation. If so, our data imply that one generation of spontaneous mutation increases the developmental time by 0.09% at 20° and by 0.04% at 25°, and reduces viability under harsh conditions, fecundity, and longevity by 1.35, 0.21, and 0.08%, respectively. Comparison of flies with none, one, and two grandfathers (or greatgrandfathers, in the case of viability) treated with EMS did not reveal any significant epistasis among the induced mutations.

Dynamic Epistasis under Varying Environmental Perturbations

“…Results from this study present an initial glimpse over environment-induced epistasis dynamics at the genome scale. Using differential epistasis from abundant-glucose to nutrient-limiting conditions, our results show that epistasis between specific genes can become more positive or more negative in nutrient-limiting conditions, which is consistent with previous findings in small scale studies [12][13][14][15][16][17][18][19][20][21][22][23]. However, we showed that, at the genome scale, epistasis is more positive in nutrient-limiting conditions.…”

“…How epistatic interactions among genes change in different environments has been intensively studied in various model organisms, including E. coli [12][13][14], S. cerevisiae [15][16][17], C. elegans [18,19] and D. melanogaster [20][21][22]. The results of these studies, however, are very controversial.…”

“…The results of these studies, however, are very controversial. While some studies observed increasing positive epistasis under harsh conditions [13,17,20], others have opposite findings [14-16, 18, 19, 21-23]. Even within the same species, different experimental studies might have conflicting conclusions (e.g.…”