Molecular cloning and partial sequence characterization of the duplicated amylase genes from Drosophila erecta

Abstract

Summary - Previous studies have shown that the a-amylase gene is duplicated in each of the 8 species comprising the Drosophila melanogaster species subgroup. In this study, a genomic library in phage lambda was prepared from the DNA of 1 species member of this subgroup, D erecta. This gene library was screened with an amylase-specific probe from the closely-related species D melanogaster. One of the cross-hybridizing phage clones was isolated, insert fragments were sub-cloned into plasmid vectors, and the identity of the cloned locus was verified by DNA sequencing. The results confirm that this species contains 2 very similar copies of the amylase-coding sequence, as does D medanogaster. Within the amylase-coding region, there is a 3% sequence divergence between the 2 species; this value rises to 6% if we consider only silent sites within the coding region. Sequence divergence between D erecta and D melanogaster in the non-coding intergenic region is approximately 15%. These results constitute the first molecular sequence data available for protein-coding genes of D erecta. The data set allows us to calculate an estimated divergence time of more than 10 million years between the 2 species. This is consistent with the results of previous phylogenetic studies. Drosophila erecta / a-amylase / molecular evolution / gene conversion