Evolutionary rewiring of bacterial regulatory networks

Abstract

Bacteria have evolved complex regulatory networks that enable integration of multiple intracellular and extracellular signals to coordinate responses to environmental changes. However, our knowledge of how regulatory systems function and evolve is still relatively limited. There is often extensive homology between components of different networks, due to past cycles of gene duplication, divergence, and horizontal gene transfer, raising the possibility of cross-talk or redundancy. Consequently, evolutionary resilience is built into gene networks - homology between regulators can potentially allow rapid rescue of lost regulatory function across distant regions of the genome. In our recent study [Taylor, et al. Science (2015), 347(6225)] we find that mutations that facilitate cross-talk between pathways can contribute to gene network evolution, but that such mutations come with severe pleiotropic costs. Arising from this work are a number of questions surrounding how this phenomenon occurs.

Keywords: bacterial motility; enhancing binding proteins; flagella regulation; gene network evolution; nitrogen regulation.

Figure 1. FIGURE 1:

Proposed two-step evolutionary model for the resurrection of flagellar motility via rewiring of the nitrogen regulation pathway.

Figure 2. FIGURE 2: Star phylogenies showing comparison of the full length

(A) protein sequence (Clustal Omega) and (B) predicted 3D structure (Neighbour joining) of RpoN-dependent EBPs in P. fluorescens SBW25. Proteins with the shortest distance travelled along lines are more similar. Note that several other proteins share closer similarity, both in sequence and structure, to FleQ (the most similar denoted by *).