Fig. 4. Targeted activation of N in R8. Arrows indicate missing ommatidia or ommatidia with too few photoreceptor cells. (A) Wild-type pattern of R8 cells labeled for Boss (top) and all photoreceptors labeled for ELAV (bottom). (B) N intracellular domain targeted to R8 with the 109-68 Gal4 line eliminates most R8 cells and other photoreceptor cells also (NEB37D). (C) Boss labeling of the spl mutant shows defects in R8 patterning (top). Elav labeling (bottom) shows both missing and incomplete ommatidia (arrows). (D) R8 and other defects comparable to spl seen when 109-68 targets R8 expression of N intracellular domain from a more weakly-expressing transgene insertion (NEB5A). (E) R8 and other defects comparable to spl seen when 109-68 targets R8 expression of full-length N. (F) R8 and other defects comparable to spl seen when 109-68 targets R8 expression of the N target gene E (spl)m.