Fig. 1. Engulfment assay using VGAL. (A-C) A syncytial-blastoderm wild-type embryo was injected with AO and VGAL and a three-dimensional, time-lapse recording was made. Shown here is a single optical section of one time point at stage 14/15 of the AO, green fluorescence (A), VGAL, red fluorescence (B) and a composite image of both fluorescent channels (C). (A-I) The engulfing macrophages are outlined with a white line. (D-F) A syncytial-blastoderm wild-type embryo was injected with AO and DQ Red BSA and a three-dimensional, time-lapse recording was made. Shown here is a projection of two 4 µm optical sections of a single time point at stage 14/15 of the AO, green fluorescence (D), DQ Red BSA, red fluorescence (E) and a composite image of both fluorescent channels (F). (G-I) A UAS-nGFP embryo was injected with caged GAL4VP16 and VGAL and a five- to eight-cell patch of cells in the ventral furrow just anterior to the cephalic furrow was photoactivated. Shown here is a projection of two 5 µm optical sections of a single time point of a stage 14/15 embryo of the GFP fluorescence (G), VGAL fluorescence (H) and a composite of both fluorescent channels (I). (J-O) A UAS-rpr; UAS-hid embryo was injected with caged GAL4VP16, AO and VGAL and a five- to eight-cell patch of cells was photoactivated in the lateral epidermis. Shown here is a series of images that are projections of three 4 µm optical sections from a time-lapse recording at 20 minute intervals from the first appearance of the AO-positive ectopic cell death. The AO signal is shown as green and the VGAL signal as red. The photoactivated region is indicated by the white circle. Notice that the position of the circle changed over time as the embryo developed. Some of the VGAL-positive spots within 10 µm of the circle originated from the photoactivated region, further VGAL-spots are from naturally dying cells outside the photoactivated zone.