Use of promoter fusions in Drosophila genetics: characterization of a YP1-ADH fusion gene.

In Drosophila melanogaster the yolk protein (YP) genes are normally expressed only in the fat body and follicular epithelium of adult females--never in males or in larvae. We describe here a first step toward a genetic examination of the developmental controls that restrict the activity of the YP genes to adult female tissues. A YP1 promoter that contains the tissue-, temporal-, and sex-specific controlling elements for expression was fused to the reporter gene, alcohol dehydrogenase (Adh). The gene fusion was transformed into an Adh-deficient genotype. As assayed by a number of criteria, that the fusion gene is expressed in the same physiological manner as the endogenous yolk protein genes. The fusion gene's activity is modulated in trans by a temperature-sensitive allele of the sex determination gene, tra-2. The Adh enzyme serves as a selectable marker and therefore these flies are suitable for use in genetic screens for trans-acting mutations that affect the expression of the yolk protein genes.