Fig. 4. Effects of altered ligand expression on embryo development. (A) Cuticle of a late embryo showing the result of ectopic UPD expression. There is abnormal retraction of the germ band and a dorsal hole (arrowhead) indicating abnormal development of the amnioserosa, whereas there is little effect on the denticle belts. (B-C) Expression of kni in the wild type (B) and in embryos with ectopic UPD expression (C). (D-F) Expression of trh in the wild-type (D), upd^– (E) and ectopic UPD embryos (F). Although the JAK/STAT pathway is required for trh expression (E), ectopic upd cannot activate trh expression outside the tracheal pits (F). (G-I) Expression of vvl in the wild-type (G), upd^– (H) and ectopic UPD embryos (I). In the wild type, expression of vvl in the hindgut is restricted to the small intestine (arrowhead in G). vvl is not expressed in the hindgut (arrowhead) of ligand-deficient mutants (H). Ectopic upd results in ectopic vvl activation in the hindgut (arrowhead in I). Df(1)os 1A was used as a deficiency for upd and related genes. (A-F) Lateral views, (G-I) dorsal views. Anterior is left in all panels. (A) Dark field image of a late embryo cuticle. (B-F) Stage 11 embryos. (G-I) Stage 13 embryos.

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