Evolution. Evolutionary resurrection of flagellar motility via rewiring of the nitrogen regulation system.
A central process in evolution is the recruitment of genes to regulatory networks. We engineered immotile strains of the bacterium Pseudomonas fluorescens that lack flagella due to deletion of the regulatory gene fleQ. Under strong selection for motility, these bacteria consistently regained flagella within 96 hours via a two-step evolutionary pathway. Step 1 mutations increase intracellular levels of phosphorylated NtrC, a distant homolog of FleQ, which begins to commandeer control of the fleQ regulon at the cost of disrupting nitrogen uptake and assimilation. Step 2 is a switch-of-function mutation that redirects NtrC away from nitrogen uptake and toward its novel function as a flagellar regulator. Our results demonstrate that natural selection can rapidly rewire regulatory networks in very few, repeatable mutational steps.
School of Biological Sciences, University of Reading, Whiteknights, Reading RG6 6AJ, UK.
Tiffany B
TB
Taylor
School of Biological Sciences, University of Reading, Whiteknights, Reading RG6 6AJ, UK.
Geraldine
G
Mulley
Department of Biology, University of Massachusetts Dartmouth, 285 Old Westport Road, North Dartmouth, MA 02747, USA.
Alexander H
AH
Dills
School of Biological Sciences, University of Reading, Whiteknights, Reading RG6 6AJ, UK. Department of Plant Production and Protection, Qassim University, Qassim, P.O. Box 6622, Saudi Arabia.
Abdullah S
AS
Alsohim
School of Biological Sciences, University of Reading, Whiteknights, Reading RG6 6AJ, UK.
Liam J
LJ
McGuffin
College of Life and Environmental Sciences, University of Exeter, Stocker Road, Exeter EX4 4QD, UK.
David J
DJ
Studholme
Department of Biology, University of Massachusetts Dartmouth, 285 Old Westport Road, North Dartmouth, MA 02747, USA.
Mark W
MW
Silby
Department of Biology, University of York, Wentworth Way, York YO10 5DD, UK.
Michael A
MA
Brockhurst
School of Biological Sciences, University of Reading, Whiteknights, Reading RG6 6AJ, UK. l.j.johnson@reading.ac.uk.
Louise J
LJ
Johnson
School of Biological Sciences, University of Reading, Whiteknights, Reading RG6 6AJ, UK. The University of Akureyri, Borgir vid Nordurslod, IS-600 Akureyri, Iceland.
Robert W
RW
Jackson
D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D005075:Biological Evolution; D005407:Flagella / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D053263:Gene Regulatory Networks; D009584:Nitrogen / Q000378:metabolism*; D011551:Pseudomonas fluorescens / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D018085:Regulon; D012641:Selection, Genetic
D001426:Bacterial Proteins; D009584:Nitrogen