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Fig. 4 Temporal control of Gal4-dependent expression using a temperature sensitive version of Gal80. Confocal maximum intensity projections, ventral views, anterior to top, 72 hours postfertilization (hpf) Tg(otpb.A:Gal4)zc67; Tg(UAS:GFP) embryos stained with anti-green fluorescent protein (GFP). A,B: Expression is indistinguishable between embryos without (A) or with (B) the Tg(elavl3:Gal80ts)zc68 transgene when raised at the restrictive temperature (28.5°C). C,D: When raised at permissive temperatures (21.5°C or 23°C) starting at 24 hpf, Gal80ts is able to effectively inhibit Gal4-dependent expression. E: When Gal4-dependent expression is initially allowed to occur from 24 to 48 hpf, shifting to the permissive temperature from 48–72 hpf allows Gal80ts to inhibit Gal4-dependent expression. F: Raising at a permissive temperature until 48 hpf, then relieving Gal80-mediated inhibition at 48 hpf permits Gal4-dependent expression to resume by 72 hpf. G,G′: Live confocal images of the same embryo before (at 24 hpf) and after (at 36 hpf) shifting to the permissive temperature, shows inhibition of Gal4-dependent expression. H: In comparison, a control embryo raised at the restrictive temperature only shows robust expression. Inset shows this same embryo at 24 hpf. Scale bar = 50 μm.