Fig. 2. bowl is required specifically at the margin for retinal triggering and hh expression. Clones are marked by the absence of GFP (A-E) or CD2 (F). (A-E) bowl^- clones spanning the posterior margin. (A, inset in B) Defective retinal initiation is associated with bowl^- mutant margin (arrow). Retinal initiation is partially rescued non-autonomously by neighboring tissue (clone outlined in B). (C,C') bowl^- clone spanning the margin loses hh-Z autonomously (arrow; clone outlined in C'). (D,D') The expression of Ptc is also reduced in a bowl^- clone (arrow). (E,E') Internal bowl^- clone abutting, but not including, the margin develops retina normally (clone outlined in E'). The hh-Z margin expression (arrow) is normal. (F,F') lines-expressing clone at the margin resembles loss of bowl, causing loss of margin hh-Z and retinal failure (arrow). The hh-Z ocellar expression is not affected (asterisk). Discs are oriented with posterior towards the right and dorsal upwards.