Experimental evidence for negative selection in the evolution of a Yersinia pestis pseudogene.
Yersinia pestis, the agent of bubonic plague, evolved from the enteric pathogen Yersinia pseudotuberculosis within the past 20,000 years. Because ancestor and descendant both exist, it is possible to infer steps in molecular evolution by direct experimental approaches. The Y. pestis life cycle includes establishment of a biofilm within its vector, the flea. Although Y. pseudotuberculosis makes biofilms in other environments, it fails to do so in the insect. We show that rcsA, a negative regulator of biofilms that is functional in Y. pseudotuberculosis, is a pseudogene in Y. pestis. Replacement of the pseudogene with the functional Y. pseudotuberculosis rcsA allele strongly represses biofilm formation and essentially abolishes flea biofilms. The conversion of rcsA to a pseudogene during Y. pestis evolution, therefore, was a case of negative selection rather than neutral genetic drift.
Sun
Yi-Cheng
YC
Program in Microbial Pathogenesis, Department of Cell and Tissue Biology, University of California, San Francisco, CA 94143, USA.
Hinnebusch
B Joseph
BJ
Darby
Creg
C
D019943:Amino Acid Substitution; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics; D018441:Biofilms / Q000254:growth & development; D017173:Caenorhabditis elegans / Q000382:microbiology; D015169:Colony Count, Microbial; D019143:Evolution, Molecular; D008954:Models, Biological; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D011544:Pseudogenes / Q000235:genetics*; D012641:Selection, Genetic; D015398:Signal Transduction; D005423:Siphonaptera / Q000382:microbiology; D015010:Yersinia pestis / Q000166:cytology / Q000235:genetics* / Q000254:growth & development
D001426:Bacterial Proteins; C074889:RcsB protein, Bacteria