An enhancer trap screen for ecdysone-inducible genes required for Drosophila adult leg morphogenesis

Although extensive studies of Drosophila imaginal disc development have focused on proliferation and patterning, relatively little is known about how the patterned imaginal discs are transformed into adult structures during metamorphosis. Studies focused primarily on leg development have shown that this remarkable transformation is coordinated by pulses of the steroid hormone ecdysone and requires the function of ecdysone-inducible transcription factors as well as proteases and components of the contractile cytoskeleton and adherens junctions. Here, we describe a genetic screen aimed at expanding our understanding of the hormonal regulation of Drosophila adult leg morphogenesis. We screened 1300 lethal P-element enhancer trap insertions on the second chromosome for a series of sequential parameters including pupal lethality, defects in leg morphogenesis, and ecdysone-induced lacZ reporter gene expression. From this screen we identified four mutations, one of which corresponds to bancal, which encodes the Drosophila homolog of hnRNP K. We also identified vulcan, which encodes a protein that shares sequence similarity with a family of rat SAPAP proteins. Both bancal and vulcan are inducible by ecdysone, thus linking the hormone signal with leg morphogenesis. This screen provides new directions for understanding the hormonal regulation of leg development during Drosophila metamorphosis.