What is it about?

When Charles Darwin described evolution by natural selection, he pictured a process that makes the different features of organisms well-suited to their environment. In the last few decades, we have learned that nature rarely tweaks organisms through direct changes to these characteristics. Rather, most evolutionary change occurs at the molecular level, through mutations in the DNA sequence that may (or may not) affect the form and functioning of an organism. Surprisingly, this partitioning of the evolutionary process between the DNA of an organism where all tiny changes occur, and the changes to visible traits that may arise as a result, is a fertile playground for evolution. Mutations frequently occur without any change to an organism’s functioning. Sometimes, such "neutral" mutations may accumulate without incident and suddenly create a surprising change due to a mutation somewhere else in the genome. In this paper, we uncover a remarkable benefit of such a two-level structure that becomes vital in a changing environment. The structure of the “mutational landscape” of an organism's DNA—i.e., the set of new DNA sequences that can be produced after mutation—can act as "recording tape" where evolution can store information about past environments, allowing populations to adapt quickly if such past environments occur again. Thus, under certain conditions, the process of mutation can be reconfigured by evolution in a way that makes adaptation more likely in the future. We also find that under these special modes of environmental change, the mutation rate can also escalate through evolution, allowing more DNA changes per generation than usual. This increased mutation rate, when combined with the reconfigured mutational landscape, allows quicker adaptation to both new environments and environments the populations have encountered in the past, shaping the evolvability of evolving populations.

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Why is it important?

Directed evolution in the lab has been used as a tool for the generation of useful biological entities ranging from novel antibodies to multicellular yeast strains. It relies primarily on natural selection, the process by which these entities are tuned to an artificial selective environment. Our work shows that it is possible to go a step further and directly optimize second-level evolutionary properties through directed evolution—specifically, the ability of evolution to produce useful variation in the future. Thus, instead of optimizing antibodies to target a single antigen, it may be possible to design antibodies that can mutate to bind to diverse targets. Alternatively, it may be possible to design bacteriophages that can evolve rapidly and can treat multiple bacterial infections at once. This multifaceted “evolution of evolvability” in a changing environment can be an incredible tool that shapes the next generation of applications of directed evolution.

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This page is a summary of: Evolution takes multiple paths to evolvability when facing environmental change, Proceedings of the National Academy of Sciences, December 2024, Proceedings of the National Academy of Sciences,
DOI: 10.1073/pnas.2413930121.
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