mutational robustness
Gros P-A & Tenaillon O 2009 Selection for chaperone-like mediated genetic robustness at low mutation rate: impact of drift, epistasis and complexity. Genetics, in press.
- ISSUE HIGHLIGHTS
- most organisms are unaffected by most mutations
- current theory predicts that such genetic robustness can be selected only in organisms having high mutation rate and population size
- genetic drift, i.e., stochastic variations of reproductive success, can be a sufficient force for robustness selection, even when the mutation rate becomes vanishingly small
- intrinsic hypothesis / by-product of the selection for non-genetic perturbations / adaptive hypothesis
- since robustness increases the tolerance to mutations, deleterious mutations can fix more easily, and the (average in time) fitness slowly decreases in return
- Deleterious?
- Fitness decrease?
- once additional deleterious mutations have been fixed, returning to lower levels of robustness is highly counterselected
- Krakauer and Plotkin (2002) study:
- when drift is strong, the population is, on average, far from the optimum, and mutation-loaded individuals benefit directly from increased robustness
- contrary to what has often been assumed, this result is independent of the mutation rate
- mutational robustness can be selected for even at a vanishing mutation rate in finite populations
- chaperone-associated robustness is likely to be costly to the cell, as it requires synthesising a new protein that itself needs many ATPs to function
- global modifiers, such as GroESL ... affects the folding of at least 250 proteins in E. coli and is required for the proper folding of 84 proteins, including 13 essential ones
- the general view of Lynch, who proposed that the apparent increase of genome complexity (measured by the genome length and gene content) observed through evolution could be explained by a congruent increase of drift
