Adaptive evolution at the molecular level of the duplicatedAmy gene system inDrosophila

Analyses of the nucleotide sequences of the duplicatedAmy genes in the eight species of theDrosophila melanogaster species subgroup have revealed concerted evolution of the coding regions and divergent evolution between the duplicated genes of the 5’-flanking regions. Homogenization between the duplicated genes in the coding region is maintained by frequent genetic exchange in various portions of the coding region. On the other hand, such genetic exchange seems to produce a large amount of DNA sequence variation and protein polymorphism at the two loci within a species. The puzzling observation that concerted evolution is restricted to the coding regions seems to be explained by not only adaptive evolution of the AMY proteins in speciation but also adaptive fixation of selectively advantageous mutations in the intergenic region that differentiate expression of the twoAmy genes. We review molecular work on theAmy gene system inDrosophila, including evidence from biochemical characterization of the AMY proteins and molecular characterization of the cis regulatory elements.