Fig 4. Omb blocks Jak/STAT signaling.

10XSTAT-GFP is a reporter of Jak/STAT signaling [76]. We added a nuclear localizing signal (nls) to obtain 10XSTAT-GFP-nls. (A) 10XSTAT-GFP-nls expression pattern (GFP, green) in wild type third instar eye disc. (B) The 10XSTAT-GFP-nls was ectopically expressed in the ventral eye margin (arrow) in an omb ^P7 hypomorphic mutant eye disc. (A, B) The position of the MF, based on the DIC image, is marked by an arrowhead. (C) STAT-lacZ is repressed by Jak/STAT signaling. In wild type late third instar eye disc, its expression was strong in the lateral poles and weaker around the DV midline, as reported [57]. (D) In l(1)omb ¹⁵ /Y eye discs, STAT-lacZ expression was attenuated in the ventral region. (E-E”’) 10XSTAT-GFP-nls (green) was ectopically induced in l(1)omb ^D4 mutant clones (clone marked by loss of RFP (red) expression and by dashed line). (E’-E”’) Higher magnification of the square marked in (E). 10XSTAT-GFP-nls was non-autonomously induced by loss of omb in the ventral margin. (F) dpp>hop+GFP caused an enlargement of the eye disc (Elav, red; GFP, green). (G) Coexpression of hop with omb (dpp>omb+hop) could largely rescue the dpp>omb phenotype (dpp-lacZ, green; Elav, red). (H-H’) Reducing STAT dosage in omb ^P7 /Y; STAT92E ³⁹⁷ /+ larvae reduced the size of the ventral retinal field compared to that in omb ^P7 /Y (Fig. 2B). Different focal planes of omb ^P7 /Y; STAT92E ³⁹⁷ /+ were shown in H and H’. The quantified eye areas are summarized in (I).