Increased gene dosage plays a predominant role in the initial stages of evolution of duplicate TEM-1 beta lactamase genes.
Gene duplication is important in evolution, because it provides new raw material for evolutionary adaptations. Several existing hypotheses about the causes of duplicate retention and diversification differ in their emphasis on gene dosage, subfunctionalization, and neofunctionalization. Little experimental data exist on the relative importance of gene expression changes and changes in coding regions for the evolution of duplicate genes. Furthermore, we do not know how strongly the environment could affect this importance. To address these questions, we performed evolution experiments with the TEM-1 beta lactamase gene in Escherichia coli to study the initial stages of duplicate gene evolution in the laboratory. We mimicked tandem duplication by inserting two copies of the TEM-1 gene on the same plasmid. We then subjected these copies to repeated cycles of mutagenesis and selection in various environments that contained antibiotics in different combinations and concentrations. Our experiments showed that gene dosage is the most important factor in the initial stages of duplicate gene evolution, and overshadows the importance of point mutations in the coding region.
Institute of Evolutionary Biology and Environmental Studies, University of Zurich, CH-8057 Zurich, Switzerland; The Swiss Institute of Bioinformatics, CH-1015 Lausanne, Switzerland; Centre for Genomic Regulation (CRG), C/Dr. Aiguader 88, 08003 Barcelona, Spain.
Riddhiman
R
Dhar
Tobias
T
Bergmiller
Andreas
A
Wagner
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D004777:Environment; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics*; D029968:Escherichia coli Proteins / Q000235:genetics*; D019143:Evolution, Molecular; D018628:Gene Dosage; D020440:Gene Duplication; D017354:Point Mutation; D012641:Selection, Genetic; D001618:beta-Lactamases / Q000235:genetics*
D000900:Anti-Bacterial Agents; D029968:Escherichia coli Proteins; D001618:beta-Lactamases
Beta lactamase; duplicate genes; experimental evolution; gene dosage