<p>SUPPLEMENTAL DATA. Supp Figure 1: Expression of so-Gal4 and sev-Gal4. </p><p>Lateral view on the head region of an so-Gal4, UAS-CD8::GFP labeled with anti-GFP</p><p>(green) and anti-FasII (red) at embryonic stage mid 10 (A) and stage 15 (C). GFP expression is detected in the optic lobe primordium (arrow) including presumptive larval</p><p>PR precursors (A) and immature PRs (C). (B) Lateral and (D) dorsal view on the head region of an sev-Gal4, UAS-CD8::GFP labeled with anti-GFP (green) and anti-FasII</p><p>(red) at embryonic stage mid 12 (B) and stage 15 (D). GFP expression is detected in immature larval PRs from the detachment of the optic lobe (arrow in B) and immature</p><p>PRs at sage 15. </p><p>Supplemental Figure 2: Expression of the Ets transcription factors Yan and Pnt during larval eye development</p><p>(A, E) Lateral view of a so-Gal4/UAS-H2B-YFP stage 11 embryonic head region stained with anti-GFP (green) and anti-Yan (red) antibodies. The region giving rise to larval PRs</p><p>(ventral/lateral tip) strongly expresses Yan (compare arrows in A and E. E shows only anti-Yan). (B, F) Dorsal view of high magnification of so-Gal4/UAS-H2B-YFP stage 15</p><p>BO labeled with anti-GFP (green), anti-Yan (red) and anti-Elav (blue) antibodies. No</p><p>Yan expression can be detected in immature larval PRs during this stage (compare arrows in B and F. F shows only anti-Yan). (C, G) Lateral view of a so-Gal4/UAS-H2B-YFP stage 11/12 embryonic head region stained with anti-GFP (green) and anti- Pnt (red) antibodies. The region giving rise to larval PRs (ventral/lateral tip) expresses Pnt</p><p>(compare arrows in C and G. G shows only anti-Pnt). (D, H) Dorsal view of high magnification of so-Gal4/UAS-H2B-YFP stage 15 BO labeled with anti-GFP (green), anti-Pnt (red) and anti-Elav (blue) antibodies. No Pnt expression can be detected in immature larval PRs during this stage (compare arrows in D and H. H shows only anti-</p><p>Pnt). </p>