Fig. 2. Vn/EGFR signalling does not delimit the notal Iro-C domain. (A-C) Domains of vn expression in second, early third and mid third instar wg^CX3/wg^CX4 wing discs, respectively. Arrowhead in B indicates initial ectopic vn expression; arrow in C, vn expression in ectopic nota. Inset: late third instar wg^CX3/wg^CX4 wing disc showing symmetrical domains of vn expression (reduced magnification). (D,E) Extent of the Iro-C domain (green; arrowheads) is essentially not affected in UAS-vein; ap-Gal4 (misexpression in the D compartment) second and third instar discs, respectively (compare with Fig. 4A,E). Wg (wing pouch marker) is in red. In parallel experiments, no significant effects were observed using the C765, tsh-Gal4, omb-Gal4, dpp^disk-Gal4 and MS1096 drivers. In E, the relatively large extent of the Wg domain in the anterior-posterior axis indicates that ap was already expressed in the dorsal compartment (Ng et al., 1996) and, therefore, that the ap-Gal4 driver was active in this disc. (F) Third instar disc overexpressing UAS-ras1^V12 in the anterior compartment (ptc-Gal4 driver). Extent of notal Iro-C domain (green; arrowhead) is unaffected. Red: Ptc marker. (G) Notal Iro-C expression (green) is inhibited and notum territory is reduced (arrowhead, compare with E or F) in UAS-raf^DN/MS-248Gal4 discs. Red: Wg marker. Inhibition of Iro-C was also observed using the driver dpp^disk-Gal4. (H,I) Expression of the MS-248Gal4 driver, as revealed by UAS-lacZ (red; separate red channel is shown in H on the right), in second and late third instar wing discs, respectively. Counterstaining: Iro-C protein (green). Note strong expression of driver in the proximal region of the discs (arrowheads).

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