Fig. 5

Fig. 5 Gal4 is a weaker transcriptional activator in zebrafish embryos than Gal4-VP16. (A–D) Single optical confocal microscopy sections (lateral view) of injected embryos at 27 hpf. Two embryos were embedded together in low-melting agarose to allow direct comparison of GFP-expression levels and number of GFP-expressing cells in a single optical section. Fluorescent (A and C, pseudocolored in green) and transmitted light (B, D) images were taken at the same focal plane without moving the embryos. (A, B) While Gal4-mRNA/UG-coinjected embryos display a broad variety of EGFPexpression, including embryos with a high frequency of EGFP-expressing cells (upper embryo), EF-G-UG-injected embryos show no or very dim EGFP fluorescence in a few cells (lower embryos). In contrast to EF-GVP-UG-injected embryos (see Fig. 3A, lower embryo), increase in laser power and contrast did not reveal an increase in the frequency of EGFP-expressing cells in EF-G-UG-injected embryos (not shown). (C, D) EF-GVP/EF-G-UG-coinjected embryos display a broad variety of EGFP expression, including embryos with strongly expressing cells in a high frequency (upper embryos), while EF-G-UG-injected embryos show no or very dim EGFP fluorescence in a few cells (lower embryo).