Fig. 1. Knockdown of EcR leads to precocious BR-Z1 expression and sensory neuron differentiation in contrast to the effects of dominant negative EcR. (A-A'') C96-GAL4 driving UAS-GFP and UAS-IR-EcR in the margin of a wing disc from a late wandering larva. In A GFP identifies areas of C96-GAL4 expression; in A'' low levels of EcR are seen in the region of GAL4 expression. A' is the merged image. (B-B'') en-GAL4 driving UAS-IR-EcR reduces the levels of EcR in the posterior compartment of a wing disc from a wandering larva (B) and leads to precocious up-regulation of BR-Z1 (B''). B' is the merged image. (C-C'') Wing disc 2-3 hours APF with MS1096-GAL4 driving the dominant negative ecdysone receptor EcR-B1^W650A. The EcR-B1 antibody also recognizes the dominant negative isoform. At 2-3 hours APF EcR-B1 is normally low, thus the label in C reflects the domain of expression of the dominant negative ecdysone receptor which blocks the up-regulation of BR-Z1 (C''). C' is the merged image. (D,D') Control disc 2 hours APF with C96-GAL4 driving UAS-GFP (D). Sensory neuron differentiation has begun in the margin as seen with 22C10 (D'). (E,E') C96-GAL4 driving UAS-GFP and UAS-IR-EcR. At 2 hours APF 22C10 labeling (E') shows advanced sensory neuron differentiation in the margin (arrows). (F,G) Sensilla on the third vein are also affected by loss of EcR function. 22C10 label shows the first axons (arrow) elongating in a 0 hour APF control (dpp-GAL4 driving UAS-GFP) disc (F). The GFP reporter shows the domain of dpp expression. (G) Axons differentiate prematurely (arrow) in a 0 hour APF disc with dpp-GAL4 driving UAS-IR-EcR. The schematic drawings indicate the morphology of the discs and the expression domain of the drivers used (stippled area). The dorsal/ventral boundary (margin) is indicated in magenta in discs from wandering larvae. In later stages the margin moves to the periphery as the disc elongates. All discs are oriented with anterior to the top and wing anlage to the right.