Molecular evolution of the Est-6 gene in Drosophila melanogaster: contrasting patterns of DNA variability in adjacent functional regions

• Published in: Gene Vol. 288; no. 1; pp. 167 - 177
• Main Authors: Balakirev, Evgeniy S., Balakirev, Elena I., Ayala, Francisco J.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 17-04-2002
• Subjects: Animals; Base Sequence; Carboxylesterase; Carboxylic Ester Hydrolases - genetics; DNA - chemistry; DNA - genetics; DNA polymorphism; Drosophila melanogaster; Drosophila melanogaster - enzymology; Drosophila melanogaster - genetics; Drosophila Proteins; Esterase-6; Evolution, Molecular; Genetic Variation; Haplotypes; Linkage Disequilibrium; Molecular Sequence Data; Multi-locus selection; Polymorphism, Genetic; Sequence Alignment; Sequence Analysis, DNA; Sequence Homology, Nucleic Acid; Time Factors; Esterase-6; Linkage disequilibrium; DNA polymorphism; Multi-locus selection; Est-6, esterase 6 gene; F, fast; S, slow; US, ultra slow; Drosophila melanogaster
• ISSN: 0378-1119; 1879-0038
• DOI: 10.1016/S0378-1119(02)00477-8

We have investigated nucleotide polymorphism at the esterase 6 gene (
Est-6) gene, including the complete coding region (1686 bp), as well as the 5′-flanking (1183 bp) and 3′-flanking (193 bp) regions of the gene, in 30 strains of
Drosophila melanogaster and in one strain of
Drosophila simulans. The level of silent variation is similar in the coding and in the 3′-flanking region, but smaller in the 5′-flanking region. Strong linkage disequilibrium occurs within each region; and also, although less pronounced, between the 5′-flanking region and the rest of the gene, including the 3′-flanking region. We suggest that the pattern of nucleotide polymorphism of
Est-6 may be shaped by: (1) directional and balancing selection acting on the promoter and the coding region; and (2) interactions between the two regions that involve variable degrees of hitchhiking. The patterns of linkage disequilibrium, as well as the statistics
Z
nS (Genetics 146 (1997)1197) and
B and
Q (Genet. Res. 74 (1999) 65), may be interpreted as there being multiple targets of selection within the gene. The previously reported
Est-6 allozyme latitudinal clines may be accounted for by the interaction between selective processes in the promoter and coding regions.