Fig. 1. Complementary expression pattern of Bar and Ato in basal undifferentiated cells. Posterior is towards the left and dorsal is upwards in all figures unless mentioned otherwise. (A) Scanning electron micrograph of adult compound eye. (B) Third instar eye disc stained with antibodies against Ato, Elav and Sens. The arrow indicates the position of the morphogenetic furrow. (C) Magnified view of B near the furrow showing four different stages of Ato expression (1-4). The 3'- and 5'-regulatory elements of ato specify the stage 1 and stages 2-4 of ato expression, respectively. (D,E) Complementary expression patterns of Bar and Ato. Longitudinal (D) and tangential (E) sections of the eye disc. Note that Bar and Ato expression is complementary in the basal cells along the furrow (D, arrow). (F) Two tier layers of eye disc. Photoreceptor and basal cell layers were stained with antibodies for Elav (red) and BarH1 (green), respectively. White and yellow arrows indicate the morphogenetic furrow and the R1/6 cells, respectively. R1 and R6 photoreceptors are labeled by both antibodies.