Krüppel-homolog, a Stage-Specific Modulator of the Prepupal Ecdysone Response, Is Essential for Drosophila Metamorphosis

Abstract We have characterised a P-element-induced prepupal mutant of Drosophila melanogaster which after an apparently normal embryonic and larval development fails to complete head eversion, an essential step in metamorphosis. The P-element insertion disrupts an ecdysone-regulated transcript which, although expressed during embryonic and larval stages, appears critical for preparing the late prepupal response to ecdysone. By a combination of molecular and genetic studies, in which we recovered new alleles, we show that the locus is complex, containing at least two distinct promoters. Its transcripts contain a short region described previously by R. Schuh et al. (1986, Cell 47, 1025–1032), who screened for homologues of the Kruppel gene. Our studies on the corresponding gene, named Kruppel-homolog ( Kr-h ), add to a growing body of evidence that specific isoforms of a number of key genes are implicated in both embryogenesis and metamorphosis.