Fig. 6. Genetic relationships between Sal and the Dpp pathway.

(A) Wild type wing. (B) sal^EPv-Gal4/+; UAS-Mad-i/UAS-GFP. The reduction in Mad expression in the sal^EPv-Gal4 domain of expression results in smaller wings that loss most of the L2, L3 and L4 veins. (C) sal^EPv-Gal4/+; UAS-Mad-i/UAS-salm. The expression of Salm under UAS control in wings with a reduction in Mad expression rescues the differentiation of the L2, L3 and part of the L4 veins. (D–I) Expression of Salm (Salm, green in D,F,H) and Dl (Dl, white in E,G,I) in wild type (D,E), sal^EPv-Gal4/+; UAS-Mad-i/UAS-GFP (F,G) and sal^EPv-Gal4/+; UAS-Mad-i/UAS-salm third instar imaginal wing discs (H,I). Note that the expression of both Salm and Dl is strongly reduced in the central region of the wing blade in F and G, the expression of Salm is strong in H, and the expression of Dl is rescued in the L3 vein in I. (J–M) No rescue by Salm of the consequences of Brk expression in the central region of the wing blade. The phenotype of sal^EPv-Gal4/UAS-GFP; UAS-brk/+ wings consists in a strong reduction of wing size and loss of the L2 and L4 veins (J). In the corresponding wing imaginal disc the expression of Salm is strongly reduced (K). The phenotype of ectopic brk expression is weakly rescued by the expression of Salm in flies of sal^EPv-Gal4/+; UAS-brk/UAS-salm genotype (L). In the corresponding wing disc, however, Salm is only expressed in a patchy pattern (M), probably due to the effects of Brk on the Gal4 driver.