Originally published as Genetics Published Articles Ahead of Print on May 15, 2006.

Genetics, Vol. 173, 1851-1869, August 2006, Copyright © 2006
doi:10.1534/genetics.105.049619

Parallel Changes in Global Protein Profiles During Long-Term Experimental Evolution in Escherichia coli

Ludovic Pelosi*, Lauriane Kühn{dagger}, Dorian Guetta*, Jérôme Garin{dagger}, Johannes Geiselmann*, Richard E. Lenski{ddagger} and Dominique Schneider*,1

* Laboratoire Adaptation et Pathogénie des Microorganismes, Université Joseph Fourier, CNRS UMR 5163, 38041 Grenoble, France, {dagger} Laboratoire Chimie des Proteines DRDC-CP, ERM 0201 CEA/INSERM/UJF, 38054 Grenoble, France and {ddagger} Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan 48824

1 Corresponding author: Laboratoire Adaptation et Pathogénie des Microorganismes, Université Joseph Fourier, CNRS UMR 5163, Institut Jean Roget, Domaine de la Merci, La Tronche 38700, France.
E-mail: dominique.schneider{at}ujf-grenoble.fr

Twelve populations of Escherichia coli evolved in and adapted to a glucose-limited environment from a common ancestor. We used two-dimensional protein electrophoresis to compare two evolved clones, isolated from independently derived populations after 20,000 generations. Exceptional parallelism was detected. We compared the observed changes in protein expression profiles with previously characterized global transcription profiles of the same clones; this is the first time such a comparison has been made in an evolutionary context where these changes are often quite subtle. The two methodologies exhibited some remarkable similarities that highlighted two different levels of parallel regulatory changes that were beneficial during the evolution experiment. First, at the higher level, both methods revealed extensive parallel changes in the same global regulatory network, reflecting the involvement of beneficial mutations in genes that control the ppGpp regulon. Second, both methods detected expression changes of identical gene sets that reflected parallel changes at a lower level of gene regulation. The protein profiles led to the discovery of beneficial mutations affecting the malT gene, with strong genetic parallelism across independently evolved populations. Functional and evolutionary analyses of these mutations revealed parallel phenotypic decreases in the maltose regulon expression and a high level of polymorphism at this locus in the evolved populations.




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