Decoupled Evolution of Coding Region and mRNA Expression Patterns After Gene Duplication : Implications for the Neutralist-Selectionist Debate

The neutralist perspective on molecular evolution maintains that the vast majority of mutations effecting gene function are neutral or deleterious. Following a gene duplication where both genes are retained, it predicts that original and duplicate genes diverge at clock-like rates. This prediction is usually tested for coding sequences, but can also be applied to another imporant aspect of gene function, the genes' expression pattern. Moreover, if both sequence and expression pattern diverge at clock-like rates, a correlation between divergence in sequence and divergence in expression patterns is expected. Duplicate gene pairs with more highly diverged sequences should also show more highly diverged expression patterns. This prediction is tested for a loarge sample of duplicated genes in the yeast Saccharomyces cerevisiae, using both genome sequence and micro array expression datea. Only a weak correlation is observed, suggesting that coding sequence and mRNA expression patterns of duplicate gene pairs evolve independently and at vastly different rates. Implications of this finding for the neutralist-selectionist debate are discussed.