Figure 5.

Notch acts upstream of abdA to promote abdominal NB death. Expression of activated N (a wor>N^icd, Dpn-red, Enh1-GFP anti-GFP green) results in increased NB number (a) and increased Enh1-GFP activity (a′). Simultaneous knockdown of abdA (b wor>N^icd, abdAi) does not decrease NB numbers (b), but profoundly influences Enh1-GFP expression (b′). This indicates that N activation of Enh1 depends on the activity of abdA. (c–f) Activated N drives greatly increased abdA expression (green) in stage 15 (c control, d wor>N^icd ) and stage 16 (e control, f wor>N^icd) embryonic NBs (Dpn-red, arrows mark co-labeled cells). Zoomed images of two regions are shown below. Conversely, knockdown of N with wor>Ni inhibits abdA expression in rescued NBs in both the central abdA domain and the more terminal AbdB domain of larvae (H abdA red, Dpn green h′ white arrows-no abdA expression in NB, green arrows-abdA expression in NB, yellow arrow- abdA expression in terminal domain). In comparison, most NBs rescued from death in MM3 larvae show abdA expression (g abdA red, dpn green, g′ abdA). (i) Quantification of abdA co-expression in NBs (+ S.D.)