Kruppel-homolog, a stage-specific modulator of the prepupal ecdysone response, is essential for Drosophila metamorphosis

We have characterised a P-element-induced prepupal mutant of Drosophila mel anogaster 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, althoug h expressed during embryonic and larval stages, appears critical for prepar ing the late prepupal response to ecdysone. By a combination of molecular a nd genetic studies, in which we recovered new alleles, we show that the loc us is complex, containing at least two distinct promoters. Its transcripts contain a short region described previously by R. Schuh et al. (1986, Cell 57, 1025-1032), who screened for homologues of the Kruppel gene. Our studie s 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 impli cated in both embryogenesis and metamorphosis. (C) 2000 Academic Press.