Fig. 3. Ectopic Ato⁺ cells form photoreceptor clusters. Bar loss-of-function clones were identified by the absence of GFP (A-I, green) or BarH1 (J-O, green) staining and marked with broken lines in C,F,I,L,O. (A-I) Ectopic Ato⁺ cells further differentiate into mature R8 photoreceptor cells within Bar loss-of-function clones. The number of cells expressing Sca (A-C; early R8 marker), Sens (D-F; early R8 marker) and Boss (G-I; late R8 marker) was increased within the clones. (J-O) Excess numbers of ommatidial clusters are formed in Bar loss-of-function clones. Photoreceptor clusters were detected by Elav (J-L) or Arm (M-O) staining. The size of some clusters within the Bar mutant clone was smaller than that of the wild-type ommatidia clusters, suggesting that photoreceptor recruitment in these ectopic clusters is not yet complete. White and yellow arrows in O indicate normal or ectopic photoreceptor clusters, respectively.