Fig 1. The EcR-B1 isoform of the EcR is the predominant isoform expressed in SC nuclei.
(A) Schematic of Drosophila male AGs and binucleate SCs and MCs within their monolayer epithelium. (B-G) Images show distal tips of AGs dissected from 6-day-old males (except for mosaic in [E]). SCs (nuclei marked by red arrows) express nuclear GFP (which also labels SC cytosol) and other transgenes under esgtsF/O control. Nuclei are stained with DAPI (blue). (B, C) Immunostaining with an antibody that cross-reacts with all EcR isoforms reveals expression in SC nuclei ([B]; red arrows) and in muscle cell nuclei ([C]; yellow arrows) but not in MCs (non-GFP-positive nuclei in [B]) in 6-day-old males. (D-F) Whereas expression of an RNAi targeting the EcR-A transcript does not affect EcR expression (F), mosaic expression of an RNAi targeting EcR-B1 transcripts ([E], green cells) or expression of an RNAi targeting all isoforms (D) strongly reduces nuclear EcR staining in SCs. In mosaics, staining is still present in non-RNAi-expressing SCs, which are not labelled with GFP ([E]; blue arrows). (G) esgtsF/O-driven expression of the EcR-B1 isoform has no detectable effect on nuclear EcR levels in SCs. Scale bars, 50 μm. AG, accessory gland; EcR, ecdysone receptor; esg, escargot; esgtsF/O, the yeast transcription factor GAL4 expressed under the control of the promoter of the gene esg in a temperature-dependent fashion; GFP, green fluorescent protein; MC, main cell; RNAi, RNA interference; SC, secondary cell.