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Following the Dynamics of Structural Variants in Experimentally Evolved Populations
Published on: February 3, 2023
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A mutational hotspot that determines highly repeatable evolution can be built and broken by silent genetic changes
James S Horton1, Louise M Flanagan2, Robert W Jackson3
1Milner Centre for Evolution, Department of Biology & Biochemistry, University of Bath, Claverton Down, Bath, BA2 7AY, UK. j.s.horton@bath.ac.uk.
Nature Communications
|October 20, 2021
Summary
Silent mutations can create or eliminate genetic hotspots, influencing bacterial evolution. This study shows how a few synonymous changes in Pseudomonas fluorescens alter mutation patterns and adaptive outcomes.
Area of Science:
- Evolutionary biology
- Microbial genetics
Background:
- Mutational hotspots are crucial for repeatable evolution but are difficult to study.
- Understanding the forces shaping mutation rate heterogeneity is key to evolutionary insights.
Purpose of the Study:
- To investigate the role of silent genetic variation in creating and breaking deterministic mutational hotspots.
- To determine how synonymous mutations affect evolutionary trajectories in Pseudomonas fluorescens.
Main Methods:
- Comparative analysis of two Pseudomonas fluorescens variants (AR2 and Pf0-2x) with differing evolutionary pathways.
- Site-specific swapping of synonymous mutations within the ntrB gene locus.
- Assessing the impact of these swaps on mutational hotspot determinism and bacterial motility restoration.
Main Results:
- The AR2 strain exhibits a highly deterministic mutational hotspot for motility restoration (>95% repeatability).
- The Pf0-2x strain shows divergent evolution due to multiple mutations, lacking a deterministic hotspot.
- Six synonymous variations in the ntrB locus were identified as responsible for this disparity, with site-swapping experiments confirming their ability to build (0% to 80%) and break (>95% to 0%) the hotspot.
Conclusions:
- Silent genetic variation, specifically synonymous mutations, plays a significant role in shaping adaptive evolution by controlling mutational hotspot determinism.
- The ntrB locus in Pseudomonas fluorescens serves as a model system to demonstrate how subtle genetic changes can profoundly alter evolutionary predictability.
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