MOLECULAR ANALYSIS OF THE INTERGENIC REGION OF THE DUPLICATED AMY-GENES OF DROSOPHILA-MELANOGASTER AND DROSOPHILA-TEISSIERI

The intergenic regions between the duplicated amylase coding regions ( Amy) of D. melanogaster and D. teissieri were sequenced. Their lengths in D. melanogaster and D. teissieri were 4,536 bp and 4,621 bp, respe ctively. Since homology between the upstream regions of the two duplic ated genes was found up to 450 bp from the initiation codon of the Amy genes, the ancestral Amy coding region duplicated together with at le ast 450 bp of the 5'-flanking region as one unit. Comparison of the re gions between the two species revealed that the level of divergence wa s very heterogeneous. Although the mean level of the nucleotide differ ence in this region was 0.107, no nucleotide substitution was found in four subregions whose sizes were more than 100 bp. Since the probabil ity of these four subregions being completely conserved between D. mel anogaster and D. teissieri was very low, these subregions were conside red to have relatively important roles in evolution. Large insertions and deletions were not observed in this region but small ones were obs erved all over the region except for an about 1-kb subregion. This 1-k b region corresponded to an open reading frame encoding a protein whic h had some sequence identity with the proteins of the serine protease inhibitor superfamily (serpin). Since we could find a transcript of th is gene and the synonymous substitution rate was higher than the repla cement substitution rate, we suggest that this gene encodes an active serpin in Dro sophila.