Evolutionary trade-off and mutational bias could favor transcriptional over translational divergence within paralog pairs

How changes in the different steps of protein synthesis – transcription, translation and degradation – contributed to differences of protein abundance among genes is not fully understood. Here, we show that yeast paralogous genes are more divergent in transcription than in translation. We explore two causal mechanisms for this predominance of transcriptional divergence: an evolutionary trade-off between the cost and precision of gene expression and a larger mutational target size for transcription. Performing simulations within a minimal model of post-duplication evolution, we find that both mechanisms are consistent with the observed divergence patterns. We also investigate how additional properties of the effects of mutations on gene expression, such as their asymmetry and correlation across levels of regulation, can shape the evolution of duplicates. Our results highlight how general trade-offs in cellular processes and mutation bias can have far-reaching impacts. If transcriptional divergence is favored between paralogs independently of gene-specific functional constraints, it may have important implications for the evolutionary potential of gene duplication and the contribution of this process to the general evolution of gene expression levels.