Tissue-autonomous EcR functions are required for concurrent organ morphogenesis in the Drosophila embryo.
The insect hormone 20-hydroxy-ecdysone (20E) peaks at different stages during the life cycle. The hormone signal is commonly transmitted by a nuclear receptor consisting of the ecdysone receptor (EcR) and Ultraspiracle (Usp, orthologous to vertebrate RXR). EcR:Usp then initiate the expression of a series of gene regulators that help mediate biological responses to the hormone. Here, we investigated the embryonic ecdysone-signalling mechanism. The rise in 20E levels that occurs at mid-embryogenesis is required for major tissue movements to complete organ morphogenesis, but the functions of EcR and Usp during embryogenesis have remained unclear. We find that both EcR and Usp are essential for head involution, dorsal closure and tracheal and midgut morphogenesis, processes that also depend on 20E, arguing that embryonic 20E signals via EcR:Usp. We also show that EcR mediates the effects on organ morphogenesis in a tissue-autonomous manner and thus, that embryonic EcR functions are not fully reflected by the commonly used EcR activity assays. Finally, we show that embryonic 20E via EcR instructs the temporal and tissue-specific expression of four transcription factors that are needed for late embryogenesis and are common to the metamorphic 20E response. The results suggest that mid-embryonic EcR-activation imparts a level of gene regulation during embryonic organogenesis that has been largely overlooked, and possibly facilitates synchronized development of individual organs.
Chavoshi
Tina M
TM
Institute of Biomedicine, Gothenburg University, P.O. Box 440, SE-40530 Gothenburg, Sweden.
Moussian
Bernard
B
Uv
Anne
A
D000483:Alleles; D000818:Animals; D030801:Animals, Genetically Modified; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004330:Drosophila / Q000196:embryology* / Q000235:genetics / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism; D046149:Embryo Culture Techniques; D018507:Gene Expression Regulation, Developmental; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D009024:Morphogenesis / Q000235:genetics*; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism; D011987:Receptors, Steroid / Q000235:genetics* / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D014132:Trachea / Q000196:embryology*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
C525044:Blimp-1 protein, Drosophila; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; C106186:Hr3 protein, Drosophila; D018160:Receptors, Cytoplasmic and Nuclear; D011987:Receptors, Steroid; D012097:Repressor Proteins; D014157:Transcription Factors; C066030:USP protein, Drosophila; C055469:ecdysone receptor; C080885:nuclear hormone receptor FTZ-F1 beta, Drosophila; C061375:Eip75B protein, Drosophila