Downregulation of the tissue-specific transcription factor Fork head by Broad-Complex mediates a stage-specific hormone response.
Drosophila development is coordinated by pulses of the steroid hormone 20-hydroxyecdysone (20E). During metamorphosis, the 20E-inducible Broad-Complex (BR-C) gene plays a key role in the genetic hierarchies that transduce the hormone signal, being required for the destruction of larval tissues and numerous aspects of adult development. Most of the known BR-C target genes, including the salivary gland secretion protein (Sgs) genes, are terminal differentiation genes that are thought to be directly regulated by BR-C-encoded transcription factors. Here, we show that repression of Sgs expression is indirectly controlled by the BR-C through transcriptional down-regulation of fork head, a tissue-specific gene that plays a central role in salivary gland development and is required for Sgs expression. Our results demonstrate that integration of a tissue-specific regulatory gene into a 20E-controlled genetic hierarchy provides a mechanism for hormonal repression. Furthermore, they suggest that the BR-C is placed at a different position within the 20E-controlled hierarchies than previously assumed, and that at least part of its pleiotropic functions are mediated by tissue-specific regulators.
Renault
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N
Institut für Genetik der Freien Universität Berlin, Arnimallee 7, D-14195 Berlin, Germany.
King-Jones
K
K
Lehmann
M
M
D000818:Animals; D002875:Chromosomes / Q000378:metabolism; D015536:Down-Regulation; D004330:Drosophila / Q000235:genetics*; D029721:Drosophila Proteins; D004441:Ecdysterone / Q000378:metabolism*; D051858:Forkhead Transcription Factors; D018507:Gene Expression Regulation, Developmental; D005967:Glue Proteins, Drosophila / Q000235:genetics / Q000378:metabolism; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism; D007814:Larva; D008297:Male; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D009928:Organ Specificity; D012469:Salivary Glands / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
C102117:Br protein, Drosophila; D029721:Drosophila Proteins; D051858:Forkhead Transcription Factors; D005967:Glue Proteins, Drosophila; D019476:Insect Proteins; D009687:Nuclear Proteins; D014157:Transcription Factors; D004441:Ecdysterone