Fig. 1. Overexpression of Ed and Nrg results in loss of photoreceptor and cone cells. Scanning electron micrographs (A-D) of adult eyes, and midpupal eye imaginal discs stained for the photoreceptor marker ELAV (red, E-H) and cone cell marker Cut (green, I-L). (A,E,I) Wild type; (B,F,J) GMR-GAL4/UAS-ed; (C,G,K) GMR-GAL4/UAS-nrg¹⁸⁰; (D,H,L) GMR-GAL4/UAS-ed/UAS-nrg¹⁸⁰. (I-L) The upper focal planes of E-H, respectively. There are seven photoreceptors (E, R8 is out of the plane of focus) and four overlying cone cells (I) in wild-type imaginal discs. Overexpression of UAS-ed in eye causes a mild rough eye (B), ommatida with six or fewer photoreceptor neurons (arrowhead in F), and ommatidia with three or fewer cone cells (J). The arrows in F and J indicate the same ommatidium that contains seven photoreceptor (F) and three cone cells (J). Overexpression of nrg¹⁸⁰ (C,G,K) alone causes no phenotype at 25°C. However, co-expression of both ed and nrg¹⁸⁰ results in a more severe rough eye phenotype (D), as manifested by reduced number of ommatidia, varying size of ommatidia and decreased number of bristles. In addition, a much higher percentage of ommatidia contain fewer photoreceptor (arrows in H) and cone cells (arrows in L).