While the presence of functionally distinct alleles that have been retained for long periods of time suggests that a simple arms race model is inadequate, there is some evidence in favor of the model. Studies of the highly variable region of R-genes involved in Avr recognition support the arms race model through evidence of adaptive evolution, suggesting that selection is driving the evolution of the variable region (LLR) of R-genes, particularly in clusters of these genes. This adaptive evolution in the LLR is consistent with an evolutionary arms race with pathogens forcing selection to continually alter their recognition specificity.

"Any new model for the evolutionary dynamics of R-genes has to account for the profound role adaptive evolution plays in R-gene selection and the maintenance of polymorphic alleles over time," said Bergelson. "We need more work to better understand short-term disease dynamics and construct new evolutionary models."

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Contact: Jeanne Galatzer-Levy
jgalatz@uchospitals.edu
773-702-6241
University of Chicago Medical Center
21-Jun-2001