The two faces of short-range evolutionary dynamics of regulatory modes in bacterial transcriptional regulatory networks

Studies on the conservation of the inferred transcriptional regulatory network of prokaryotes have suggested that specific transcription factors are less-widely conserved in comparison to their target genes. This observation implied that, at large evolutionary distances, the turnover of specific transcription factors through loss and non-orthologous displacement might be a major factor in the adaptive radiation of prokaryotes. However, the recent work of Hershberg and Margalit((1)) suggests that, at shorter phylogenetic scales, the evolutionary dynamics of the bacterial transcriptional regulatory network might exhibit distinct patterns. The authors find previously unnoticed relationships between the regulatory mode (activation or repression), the number of regulatory interactions and their conservation patterns in gamma-proteobacteria. These relationships might be shaped by the differences in the adaptive value and mode of operation of different regulatory interactions.