Phenotype switching of the mutation rate facilitates adaptive evolution

Area of Science:

• Evolutionary biology
• Genetics
• Molecular biology

Background:

• Mutation rate is crucial for adaptive evolution and can be altered by specific alleles.
• Emerging evidence suggests mutation rates can vary within genetically identical individuals due to factors like expression noise and translation errors.
• This variation may be heritable epigenetically, creating a mutator phenotype independent of genetic mutations.

Purpose of the Study:

• To mathematically investigate how the rate of adaptive evolution is influenced by the switching rate between mutation rate phenotypes.
• To model the impact of non-genetic inheritance of mutation rate on evolutionary trajectories.

Main Methods:

• Mathematical modeling of an asexual population with two phenotypes: non-mutator and mutator.
• Analysis of offspring's potential to switch mutation rate phenotypes from their parents.
• Evaluation of adaptation rates on artificial and natural fitness landscapes under varying switching rates.

Main Results:

• Empirically relevant switching rates for non-genetic inheritance significantly increase adaptation rates.
• These rates facilitate the simultaneous maintenance of mutator phenotypes and intermediate mutations, aiding adaptation.
• Non-genetic inheritance boosts the proportion of mutators, increasing hitchhiking of the mutator phenotype with adaptive mutations and facilitating further adaptation.

Conclusions:

• Non-genetic inheritance of mutation rate phenotypes, driven by factors like expression noise, can substantially enhance evolutionary adaptation.
• This mechanism provides a plausible explanation for observed protein expression noise affecting mutation rates.
• Epigenetic inheritance of mutation rate phenotypes offers a novel pathway to facilitate adaptive evolutionary processes.