(A) Diagram of the bidirectional tetracycline response element (biTRE)-containing construct injected into Tg(Xla.rho:rtTAflag) one-cell embryos. EGFP and mCherry with a nuclear localization sequence (nls-mCherry) flank the biTRE. (B–G) Confocal z-projections of retinal sections from injected Tg(Xla.rho:rtTAflag) larvae at 6 dpf labeled with anti-FLAG antibody (blue). (B–D) GFP fluorescence (B, green) and nls-mCherry fluorescence (C, red) are undetectable in the absence of doxycycline (Dox) treatment, while anti-FLAG labeling (D, blue) is visible in rod photoreceptors. (E–G) GFP fluorescence (E, E′, green) and nls-mCherry fluorescence (F, F′, red) are visible in the photoreceptor layer and co-localize with anti-FLAG labeling (G, G′, blue) in the rod photoreceptors after 48 h Dox treatment. Boxed regions in E, F, and G correspond to E′, F′, and G′. dA, polyadenylation sequence; Tol2, pTol integration site. Scale bar (G), 50 µm.