Fig. 4. Absence of Ed from the roof cells generates an endogenous Ed expression border. (A,B) Cross-sections (lateral view) through the dorsal anterior follicular epithelium at early (A) and late (B) stage 11. Ed (red) is detected in cells expressing the rho-lacZ floor cell marker (green). The floor cell shown in A has begun to elongate posteriorly; this elongation is more pronounced by the stage shown in B. Nuclei are shown in blue. (C-C'') Stage 11 (dorsal view).(C) High Broad levels mark the roof cell nuclei. (C') Ed is present in all follicle cells except for two dorsolateral domains. (C'') Merge. Ed (red) is absent from the roof cells (green); one roof cell domain is outlined. (D-D'') Stage 11 (dorsal view). The two L-shaped floor cell domains (D, basal confocal section) align with the limit of the Ed domain (D', apical confocal section). (D'') Merge of Ed (red) and rho-lacZ (green). The patterns in merged images (C'',D'') are slightly out of register owing to the different planes of the images and the onset of morphogenesis (see A).