title: The role of ecdysone in the induction and maintenance of hsp27 transcripts during larval and prepupal development of Drosophila.
abstract: The Drosophila melanogaster small heat-shock gene hsp27 carries the canonic ecdysone response element (EcRE) at -537. This EcRE has been used extensively both in cultured cells and in vitro for studies of the ecdysone response. We have characterised the developmental expression of hsp27 in wild-type larval and prepupal salivary glands in parallel with that of the E74B and E74A primary ecdysone response transcripts, which are induced in the mid and late third larval instar by a minor and major increase in ecdysone titre respectively. The induction of hsp27 occurs between these two events in larvae and in parallel with that of E74A in prepupae. Transcript levels are severely reduced in ecd1 and dor (22) (deep orange) mutant larvae but are only moderately reduced in larvae mutant for the Broad-Complex allele br (t435) . By culturing salivary glands of different ages with low (1.8×10(-8) M) or high (1.8×10(-6) M) concentrations of hormone, we show that the response of an EcRE varies during development and that the timing of the response cannot be predicted solely from its apparent strength in cell line analyses.
authors.affiliation: Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS/INSERM/ULP, BP 163-F-67404 Illkirch Cedex, Strasbourg, France, , , , , , FR.
authors.forename: F
authors.initials: F
authors.lastname: Huet
authors.forename: J L
authors.initials: JL
authors.lastname: Lage
authors.forename: C
authors.initials: C
authors.lastname: Ruiz
authors.forename: G
authors.initials: G
authors.lastname: Richards