(A) Diagram of the construct used to generate the stable transgenic zebrafish line, Tg(opn1sw1:rtTAflag); alb−/−, which expresses a FLAG-tagged rtTA protein specifically in UV cone photoreceptors. The UV opsin promoter (opn1sw1) drives expression of the flag-epitope tagged reverse tetracycline-controlled transcriptional activator (rtTAflag) gene. (B, C) Confocal z-projection of a retinal section from a 6 dpf Tg(opn1sw1:rtTAflag); alb−/− larva labeled with anti-FLAG and anti-UV opsin antibodies. (B) Anti-FLAG immunofluorescence (green) is visible in the photoreceptor layer of the retina. (C) Anti-UV opsin immunofluorescence (red) colocalizes with the anti-FLAG immunofluorescence (green) in UV opsin cone photoreceptors. dA, polyadenylation signal; Tol2, pTol integration site. Scale bar (C), 50 μm.