Fig. 2. The L5 primordium forms within the omb domain adjacent to brk-expressing cells. (A) A third instar wing imaginal disc triple labeled for Kni protein (red), Dl protein (blue) and sal-lacZ expression (green, ß-Gal). (B) sal-lacZ (ß-Gal) channel alone for the disc shown in A. (C) Kni and Dl channels for the disc shown in A. Kni is expressed anterior to cells expressing high levels of sal, but there is a significant gap between the posterior edge of the sal expression domain and the L5 primordium. (D) A third instar wing imaginal disc triple labeled for Kni protein (red), Dl protein (blue) and omb-lacZ expression (green, ß-Gal). (E) omb-lacZ (ß-Gal) channel alone for the disc shown in D. (F) Kni and Dl channels for disc shown in D. omb expression extends well past the Kni L2 stripe anteriorly, but just includes the L5 primordium posteriorly. (G) A third instar wing imaginal disc triple labeled for Kni protein (red), Dl protein (blue) and brk-lacZ expression (green, ß-Gal). (H) brk-lacZ (ß-Gal) channel alone for the disc shown in G. (I) Kni and Dl channels for disc shown in G. The L5 primordium lies along the outside border of the high level brk expression domain. (J) A third instar wing imaginal disc of omb-lacZ flies, double labeled for ß-Gal protein (brown) and ab RNA (blue, arrowhead). The ab stripe runs just within the domain of strong omb expression. (K) A third instar wing imaginal disc of brk-lacZ flies, double labeled for ß-Gal protein (brown) and ab RNA (blue, arrowhead). The ab stripe runs just adjacent to the domain of strong brk expression.