The environment plays a key role in shaping gene regulatory network (GRN) arrangement, with natural selection able to make adjustments to specific interactions. However, we do not yet understand the evolutionary processes that create and constrain opportunities for GRN adaptation and expansion. Our model organism is a genetically modified Pseudomonas fluorescens SBW25 mutant, which is non-motile and non-flagellate by deletion of the master regulator of flagellar synthesis (fleQ) and a transposon-insertion disrupting viscosin production. We have shown that under ecological conditions that imposed strong selection for dispersal, these immotile bacteria re-evolved flagellar motility within 96 hours via a repeatable, two-step evolutionary pathway. A switch-of-function mutation allowed NtrC, a distant homologue of FleQ, to commandeer control of the fleQ regulon, which putatively increased affinity for FleQ target genes but decreased affinity for NtrC target genes. The evolved NtrC combines its pre-existing nutritional regulatory function with a novel function as a flagellar regulator, but there is a trade-off between these two roles. This trade-off shapes the opportunity for rewiring between networks and constrains evolutionary routes in different nitrogen environments. Our results demonstrate the role of environmental drivers in creating opportunities for recruitment of novel gene regulators – a central process in GRN expansion and adaptation.
|Publication status||Published - 5 Sep 2017|
|Event||International Conference on Pseudomonas - Liverpool, Liverpool, UK United Kingdom|
Duration: 5 Sep 2017 → 9 Sep 2017
|Conference||International Conference on Pseudomonas|
|Country/Territory||UK United Kingdom|
|Period||5/09/17 → 9/09/17|