Evolutionary trajectories of new duplicated and putative de novo genes.

The formation of new genes during evolution is an important motor of functional innovation, but the rate at which new genes originate, and the likelihood that they persist over longer evolutionary periods, are still poorly understood questions. Two important mechanisms by which new genes arise are gene duplication and de novo formation from a previously non-coding sequence. Does the mechanism of formation influence the evolutionary trajectories of the genes? Proteins arisen by gene duplication retain the sequence and structural properties of the parental protein and thus they may be relatively stable. Instead, de novo originated proteins are often species-specific and thought to be more evolutionary labile. Despite these differences, here we show that both types of genes share a number of similarities, including low sequence constraints in their initial evolutionary phases, high turnover rates at the species level and comparable persistence rates in deeper branchers, both in yeast and flies. In addition, we show that putative de novo proteins have an excess of substitutions between charged amino acids compared to the neutral expectation, which is reflected in the rapid loss of their initial highly basic character. The study supports high evolutionary dynamics of different kinds of new genes at the species level, in sharp contrast with the stability observed at later stages.