Directed evolution of a duplicated fluorescent protein

Gene duplication is a fundamental driving force of molecular evolution In this work, we expressed a fluorescent protein in one or two copies in Escherichia coli (E. coli) and subjected it to multiple rounds of directed evolution under different conditions. We then analyzed the evolving populations at both the genotypic and phenotypic level . We observed that in the early stages of evolution, populations carrying two gene copies displayed higher mutational robustness compared to those carrying a single gene copy. As a consequence, populations with two copies experienced relaxed purifying selection, evolved higher phenotypic and genetic diversity, carried more mutations and accumulated combinations of key mutations earlier than the control populations with one copy.