Convergent evolution of gene networks by single‐gene duplications in higher eukaryotes

By combining phylogenetic, proteomic and structural information, we have elucidated the evolutionary driving forces for the gene‐regulatory interaction networks of basic helix–loop–helix transcription factors. We infer that recurrent events of single‐gene duplication and domain rearrangement repeatedly gave rise to distinct networks with almost identical hub‐based topologies, and multiple activators and repressors. We thus provide the first empirical evidence for scale‐free protein networks emerging through single‐gene duplications, the dominant importance of molecular modularity in the bottom‐up construction of complex biological entities, and the convergent evolution of networks.