Abstract
BackgroundBiological phenotypes are described as “canalized” if they are robust to minor variation of environment and/or genetic background. The existence of a robust phenotype logically implies that some underlying mechanism must be variable, in the sense of “able to vary”, in order to compensate for variation in the environment and/or genetic effects. Several lines of evidence lead to the conclusion that deleterious mutations predictably render morphological, developmental, and life-history traits more sensitive to small random environmental perturbations - that is, mutations de-canalize the phenotype.Methodology/Principal FindingsUsing conventional dye-swap microarray methodology, we compared transcript abundance in a sample of >7,000 genes between four mutation accumulation (MA) lines of the nematode Caenorhabditis elegans and the common (unmutated) ancestor. There was significantly less environmental variance in the MA lines than in the ancestor, both among replicates of the same gene and among genes.Conclusions/SignificanceDeleterious mutations consistently decrease the within-line component of variance in transcript abundance, which is straightforwardly interpreted as reducing the sensitivity of gene expression to small random variation in the environment. This finding is consistent with the idea that underlying variability in gene expression might be mechanistically responsible for phenotypic robustness.
Highlights
One of the hallmarks of animal development is its robustness to small environmental and genetic perturbations. This robustness is often called ‘‘canalization’’ [1,2,3], by which it is meant that the same phenotypic trait develops under disparate environmental conditions or in different genetic backgrounds
We recently reported a study in which we quantified the change in VE for fitness and body size with spontaneous mutation accumulation in three species of nematodes in the family rhabditidae [7]
As part of a comprehensive effort to characterize the cumulative effects of spontaneous mutations on environmental variance, we re-analyzed the data of Denver et al [12], in which transcript abundance was measured in four lines of C. elegans in which mutations had accumulated for,280 generations and in the common ancestor of the mutation accumulation (MA) lines
Summary
One of the hallmarks of animal development is its robustness to small environmental and genetic perturbations. Conclusions/Significance: Deleterious mutations consistently decrease the within-line component of variance in transcript abundance, which is straightforwardly interpreted as reducing the sensitivity of gene expression to small random variation in the environment.
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