|
|
|
|
|
|
|
||||
| Home Help Feedback Subscriptions Archive Search Table of Contents | ||||
Howard Hughes Medical Institute, Department of Human Genetics, University of Utah, 15 North 2030 East Room 5100, Salt Lake City, UT 84112-5331, USA
*Author for correspondence (e-mail: carl.thummel{at}genetics.utah.edu)
Accepted 4 January 2002
Ecdysteroid signaling in insects is transduced by a heterodimer of the EcR and USP nuclear receptors. In order to monitor the temporal and spatial patterns of ecdysteroid signaling in vivo we established transgenic animals that express a fusion of the GAL4 DNA binding domain and the ligand binding domain (LBD) of EcR or USP, combined with a GAL4-dependent lacZ reporter gene. The patterns of ß-galactosidase expression in these animals indicate where and when the GAL4-LBD fusion protein has been activated by its ligand in vivo. We show that the patterns of GAL4-EcR and GAL4-USP activation at the onset of metamorphosis reflect what would be predicted for ecdysteroid activation of the EcR/USP heterodimer. No activation is seen in mid-third instar larvae when the ecdysteroid titer is low, and strong widespread activation is observed at the end of the instar when the ecdysteroid titer is high. In addition, both GAL4-EcR and GAL4-USP are activated in larval organs cultured with 20-hydroxyecdysone (20E), consistent with EcR/USP acting as a 20E receptor. We also show that GAL4-USP activation depends on EcR, suggesting that USP requires its heterodimer partner to function as an activator in vivo. Interestingly, we observe no GAL4-LBD activation in the imaginal discs and ring glands of late third instar larvae. Addition of 20E to cultured mid-third instar imaginal discs results in GAL4-USP activation, but this response is not seen in imaginal discs cultured from late third instar larvae, suggesting that EcR/USP loses its ability to function as an efficient activator in this tissue. We conclude that EcR/USP activation by the systemic ecdysteroid signal may be spatially restricted in vivo. Finally, we show that GAL4-EcR functions as a potent and specific dominant negative at the onset of metamorphosis, providing a new tool for characterizing ecdysteroid signaling pathways during development.
Key words: Nuclear receptor, Metamorphosis, Ecdysteroid, Gene regulation, Steroid signaling, Drosophila
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati 
Twitter What's this?
This article has been cited by other articles:
|
|
 |
|
  J. Sun, L. Smith, A. Armento, and W.-M. Deng Regulation of the endocycle/gene amplification switch by Notch and ecdysone signaling J. Cell Biol., September 8, 2008; 182(5): 885 - 896. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 K. D. Baker, R. B. Beckstead, D. J. Mangelsdorf, and C. S. Thummel Functional interactions between the Moses corepressor and DHR78 nuclear receptor regulate growth in Drosophila Genes & Dev., February 15, 2007; 21(4): 450 - 464. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 L. Palanker, A. S. Necakov, H. M. Sampson, R. Ni, C. Hu, C. S. Thummel, and H. M. Krause Dynamic regulation of Drosophila nuclear receptor activity in vivo Development, September 15, 2006; 133(18): 3549 - 3562. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Schubiger, C. Carre, C. Antoniewski, and J. W. Truman Ligand-dependent de-repression via EcR/USP acts as a gate to coordinate the differentiation of sensory neurons in the Drosophila wing Development, December 1, 2005; 132(23): 5239 - 5248. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. Luria and J. D. Furlow Spatiotemporal retinoid-X receptor activation detected in live vertebrate embryos PNAS, June 15, 2004; 101(24): 8987 - 8992. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T. Kozlova and C. S. Thummel Essential Roles for Ecdysone Signaling During Drosophila Mid-Embryonic Development Science, September 26, 2003; 301(5641): 1911 - 1914. [Abstract] [Full Text] [PDF]
|
|
