Insertion of the retroposable element, jockey, near the Adh gene of Drosophila melanogaster is associated with altered gene expression

Abstract

The alcohol dehydrogenase (Adh) gene of Drosophila melanogaster is well suited to be a gene expression reporter system. Adh produces a measurable phenotype at both the enzyme and mRNA levels. We recovered a spontaneous transposable element (TE) insertion mutation near the Adh gene. The insertion is a truncated retroposable element, jockey, inserted upstream of the adult Adh enhancer region. Comparisons between the Adh(jockey) allele and its direct wild-type ancestral allele were made in an isogenic background (i.e. identical cis and trans factors). Differences in Adh(jockey) expression compared with the wild-type can be attributed solely to the presence of the jockey element. This jockey insertion results in a decrease in adult mRNA transcript levels in the Adh(jockey) homozygous lines relative to the wild-type counterpart and accounts for a correlated decrease in alcohol dehydrogenase (ADH) enzyme activity. The larval ADH activity levels are not detectably different.