Fig. 4. Iro-C helps to specify the Drosophila notum and establishes a pattern organizer at the notum/wing hinge border. (A) Cartoon of a mature wing disc with indication of the fates of the relevant regions. Dark and light blue lines indicate compartment borders (D, dorsal; V, ventral; A, anterior; P, posterior compartments). Iro-C domain of expression is coextensive with the presumptive notum in young wing discs. This expression is necessary for the specification of the notum, as Iro-C- clones transform notum into wing hinge (Diez del Corral et al., 1999; indicated by a green H). The border of notum Iro-C-expressing and hinge Iro-C-non-expressing cells is a pattern organizing center (arrows), as revealed by the effects of Iro-C- clones on the surrounding wild-type tissue. This acquires properties of lateral notum (LN; see also below). (B) Clones of cells overexpressing Ara in the wing pouch stained with anti Ara antibody (red in the A compartment and white in the P compartment). The cells show strong affinity for each other, as indicated by the string-like shape of the clones that can establish contact even across the A/P compartment boundary (arrowhead). Blue and white, engrailed expression (data courtesy of R. Diez del Corral). (C) Iro-C- clone (iroDFM3) on which the cartoon in A has been modeled. Green: l(2)09261 marker specific for the wing, hinge and anterior lateral notum (arrowhead). This marker is not or is very weakly expressed in the rest of the presumptive notum. The presence of the Iro-C- clone (asterisk) causes the surrounding wild-type tissue to express the marker (arrow), indicating a fate transformation towards lateral notum. (Data taken from Diez del Corral et al., 1999.)
