Figure 4
Dl overexpression in R8 cells A. Overexpressing Dl in differentiating R8 cells leads to a rough eye of similar size to wild type (699 ± 21 ommatidia were recorded in male eyes and 790 ± 49 in females). Genotype is male 109-68>DESI (line A10). Overexpressing Dl in spl heterozygotes was similar (not shown; 693 ± 47 facets per eye were counted in spl/+; 109-68>A10 females, compared with 790 ± 49 in +/+;109-68>A10 females). 109-68 drives expression in R8 cells from column 1 onwards[54], too late to affect initial R8 specification but possibly in time to affect abnormal ommatidium development that occurs in spl mutants[7]. B. 109-68>DESI (line A10) eye discs labelled for the R8-specific Boss protein (green) and photoreceptor protein elav (magenta). No ommatidia or R8 cells were obviously missing as a result of Dl overexpression, nor were ectopic R8 cells seen. C. spl/Y; UAS DESI (line A10) males showed the small, rough eye typical of spl (386 ± 54 ommatidia). The Dl transgene is expected to remain unexpressed in this background. D. spl/Y; UAS DESI (line A10) eye discs show the typical spl phenotype. Some R8 cells and ommatidia are missing, other ommatidia have abnormal R8 cells and lack other photoreceptor cells[7]. E. spl/Y; 109-68>DESI (line A10) eyes. Dl overexpression in R8 cells did not rescue the spl mutant. In fact there was a statistically insignificant tendency for eyes tended to appear smaller than inspl. (312 ± 101 ommatidia were counted in spl/Y; 109-68> A10 male eyes). F. spl/Y; 109-68>DESI (line A10) eye discs also resembled spl. No rescue of the R8 or outer photoreceptor defects was apparent.