Direct and widespread role for the nuclear receptor EcR in mediating the response to ecdysone in Drosophila

Ecdysone signaling has long been studied as a paradigm for how hormones can synchronize development events in tissues throughout the animal. At the genetic level, ecdysone acts through its receptor, EcR, which has been classically thought to act at a relatively small number of canonical, ecdysone-responsive genes which then go on to activate the effectors of cellular processes. However, in spite of the decades of work studying EcR, the understanding of how EcR promotes changes in gene expression genome-wide in vivo remains incomplete. To examine EcR's role in promoting changes in gene expression, we use a tissue-specific GAL4 driver to knockdown EcR throughout wing development and perform RNAseq on both WT wings and EcR-RNAi wings at -6h after puparium formation (APF) and +6hAPF. We find that EcR is required to promote thousands of gene expression changes genome-wide. To determine whether EcR is directly effecting these changes, we perform CUT&RUN in wings to identify EcR binding sites genome-wide. We find that EcR directly binds thousands of sites genome-wide, including many genes important for wing development. Collectively, these data suggest that EcR does not only act the top of a signaling cascade, but, instead, directly effects the response to ecdysone at multiple levels. Overall design: Total-RNAseq from wing tissue at -6hAPF (3rd larval wandering, 3LW) and +6hAPF in WT and EcR-RNAi genotypes; CUT&RUN from WT wing tissue at -6hAPF and +6hAPF