Fig. 2. Ligand regulation of GAL4-LBD fusion protein activity. GAL4-LBD activation patterns are shown for three receptors in a wild-type background (wt; A,E,I) or disembodied mutant background (dib; B,F,J), in culture in either the absence (C,G,K) or presence of 5 µM 20-hydroxyecdysone (20E; D,H,L). GAL4-EcR is active in the amnioserosa of stage 14 wild-type embryos (A), but not in dib mutant embryos (B). Culturing in the presence of 20E induces ectopic activation in the epidermis (C,D). GAL4-FTZ-F1 is active in the yolk nuclei of embryos at stage 13 (E,F) and stage 16 (G,H) and is unaffected in a dib mutant background (F) or by the presence of exogenous 20E (H). GAL4-DHR38 is active in the epidermis and amnioserosa of stage 13 embryos (I,J) and is not affected in a dib mutant background (J, compare with K). The activity of GAL4-DHR38 in stage 17 cultured embryos is upregulated by exogenous 20E (L). The activity of GAL4-DHR96 in stage 13 embryos (M) is significantly increased by the addition of 5x10^-6 M CITCO (N).