A Tirant insertion in the alcohol dehydrogenase locus of Drosophila melanogaster

Abstract

An alcohol dehydrogenase allele Adh AAS44 isolated from an Australian natural population of Drosophila melanogaster is associated with low activity in adult flies. A 5.0 kb insertion in the first intron between the distal and proximal promoters has been partially sequenced and shown to be homologous to the retrotransposon Tirant. The insertion is the major change in the transcriptional unit of Adh AAS44 , but there is also a single nucleotide change in the adult Adh enhancer. The main phenotypic effect associated with the Tirant insertion is a reduction in alcohol dehydrogenase activity and transcript level in adult flies. There is a very much smaller reduction in 3rd instar larvae. The data indicate that Tirant affects transcription from the distal promoter. The possible mechanisms for this differential effect on transcription are discussed.