Convergent evolution of regulation of dctA by two distantly-related response regulators. From the gene trees (not shown), we identified subfamilies that correspond to dctA, dcuR, and arcA. For example, we split arcA and its relatives from the closely related torR subfamily of response regulators, which is also present in many γ-Proteobacteria. We show the presence and absence of these subfamilies within the γ-Proteobacteria. The coexistence of dcuR and dctA in the genome is relatively recent, which shows that this regulation evolved after dcuR diverged from arcA.