The Drosophila aeroplane mutant is caused by an I-element insertion into atissue-specific teashirt enhancer motif

In Drosophila melanogaster, aeroplane (ae) is a regulatory allele of teashi rt (tsh), and the mutant wing posture phenotype of homozygous ae flies is c aused by a defect in the hinge region of the wing, whereby the base of the wing at the proximal ventral radius is fused to the thorax in the region of the pleural wing process. The apparent paralysis of the wings and the droo ping halteres are caused by an I-element insertion into a 3' noncoding sequ ence of tsh. The cis-acting regulatory element interrupted by the I element is required, to drive tsh expression in the regions of the developing adul t that give rise to proximal wing and haltere tissues. Loss of this express ion results in the fusion of the proximal structures of the wing and halter es to the thoracic cuticle. Further characterization of this tsh regulatory motif has now identified an additional enhancer activity directing tsh exp ression in tissues forming portions of the midgut. Subdivision of this midg ut enhancer activity has identified putative negatively acting motifs.