Gene sharing during enzyme recruitment reveals distinct adaptive strategies including massive, sustained duplication without divergence

The Innovation-Amplification-Divergence model posits that single multifunctional enzymes evolve into multiple monofunctional enzymes through two events: First, selective pressure on a multifunctional enzyme leads to a duplication of the gene encoding that enzyme in an organism's genome. Second, the duplicate gene copy can freely accumulate mutations that enhance one of the encoded enzyme's functions while the original copy can accumulate mutations that enhance the enzyme's other encoded function. Intriguingly, our results reveal sequence divergence only in cells that experience mild amplification, and no divergence in cells that experience massive amplification. This suggests that sequence divergence may be suppressed above a certain number of gene copies, providing a new perspective on a widely accepted theory of evolution.