title: The contribution of spontaneous mutation to variation in environmental responses of Arabidopsis thaliana: responses to light.
abstract: It has been hypothesized that new, spontaneous mutations tend to reduce fitness more severely in more stressful environments. To address this hypothesis, we grew plants representing 20 Arabidopsis thaliana mutation-accumulation (M-A) lines, advanced to generation 17, and their progenitor, in differing light conditions. The experiment was conducted in a greenhouse, and two treatments were used: full sun and shade, in which influx of red light was reduced relative to far-red. The shade treatment was considered the more stressful because mean absolute fitness was lower in that treatment, though not significantly so. Plants from generation 17 of M-A developed significantly faster than those from generation 0 in both treatments. A significant interaction between generation and treatment revealed that, counter to the hypothesis, M-A lines tended to have higher fitness on average relative to the progenitor in the shaded conditions, whereas, in full sun, the two generations were similar in fitness. A secondary objective of this experiment was to characterize the contribution of new mutations to genotype x environment interaction. We did not, however, detect a significant interaction between M-A line and treatment. Plots of the line-specific environmental responses indicate no tendency of new mutations to contribute to fitness trade-offs, between environments. They also do not support a model of conditionally deleterious mutation, in which a mutant reduces fitness only in a particular environment. These results suggest that interactions between genotype and light environment previously documented for A. thaliana are not explicable primarily as a consequence of steady input of spontaneous mutations having environment-specific effects.
authors.affiliation: Monsanto Company, Madison, Wisconsin 53562, USA.
authors.forename: Christina M
authors.initials: CM
authors.lastname: Kavanaugh
authors.forename: Ruth G
authors.initials: RG
authors.lastname: Shaw
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development*; D004777:Environment; D014644:Genetic Variation; D005838:Genotype; D008027:Light; D008957:Models, Genetic; D009154:Mutation / Q000235:genetics*; D012044:Regression Analysis; D012641:Selection, Genetic