Fig. 6. Dl and Ser signaling in the wing pouch needs ubiquitin ligase activity.
(A-H) Wg (red) in wing pouches carrying mutant clones marked by the expression
of GFP (green). In all panels, ventral is downwards. Scale bar: 40 µm; 60
µm in D,G. (A,B) Clones overexpress UAS-Dl in a wild-type (A) or
mib1 (B) background. Whereas ectopic Wg is induced by dorsal and
(less) by ventral (arrows) clones in A, no Wg induction is observed in B. The
endogenous Wg stripe is abolished (arrowhead); this is also observed in
mib1 clones without Dl overexpression (data not shown). (C)
mib1 clones overexpressing UAS-Dl together with
UAS-neur restore Wg induction; in fact Dl activity in the ventral
compartment is enhanced (arrows, compare with A). (D,E) Clones overexpress
UAS-Ser in a wild-type (D) or mib1 (E) background. Ser
induces Wg exclusively in the ventral compartment (D), but not when expressed
in mib1 cells (E). (F) Ser regains its activity to induce Wg in a
mib1 background, if it is co-expressed with UAS-neur. Ser
cannot induce Wg in the dorsal compartment, irrespective of the presence of
ubiquitin ligases (D,F; arrowheads), probably owing to high Fng levels. (G)
Co-expression of UAS-Dl with UAS-neur
R in a
wild-type background efficiently induces ectopic Wg in both compartments,
indicative of increased Dl activity (compare with A). (H) This is abolished by
loss of mib1. (I) Cut is imaged (red), which is a nuclear marker for
the DV boundary. mib1 mutant clones are marked by the absence of GFP.
UAS-Dl is overexpressed via ptc-Gal4, which drives
expression just anterior of the anteroposterior boundary (white line). In the
cells posteriorly adjacent to this expression domain (to the right of the
white line), ectopic Cut is detected within mib1 cells if they abut
anterior wild-type cells (arrow), but not if they abut mutant anterior cells
(arrowhead). Inset shows an enlargement of the boxed area; the Cut-positive
nuclei, which do not contain GFP appear red. The presence of these
Cut-positive mib1 mutant cells suggests that
mib1+ is not needed for signal reception.