Figure 5. Mosaic expression of spineless in the developing retina.

a, In situ hybridization of a whole-mount pupal retina with an antisense ss probe (green) and an ELAV antibody (blue). ss expression can be observed in all bristle cells (asterisks), as well as in one PR (circles) per ommatidium in only 60–80% of all ommatidia. Note that ss levels vary from cell to cell. b, The PR cell positive for ss (green) is identified as an R7 cell by co-staining with the R7-specific marker Prospero (Pros, red). Neurons are marked with ELAV (blue). c, Nuclear β-gal (nβ-Gal, red) driven under the control of ss_eye-Gal4 reveals mosaic expression of ss in one cell per cluster. Neurons are marked with ELAV (blue). Dorsal is to the left in all panels.