Fig. 7. The consequences of ectopic expression of dve. (A-D,F,G) Wing
imaginal discs bearing clones of UAS-dve expressing cells in the wing
area. The Dve-expressing clones were induced with help of the Flip-out method,
using hsFlp and the AyGal4-UAS-GFP constructs, during the second larval instar
stage and labelled by the green fluorescence of the GFP. Expression of all
genes is detected by antibody staining. (A-C) Expression of
dveP1738-lacZ and Nub in a wing imaginal disc
bearing Dve-expressing clones. (A) Expression of
dveP1738-lacZ. (B) Expression of Nub. (C) The
same wing imaginal disc as shown in A and B, showing the Dve-expressing clones
in green, expression of Nub in blue and expression of
dveP1738-lacZ in red. Several effects are
observed. First, clones in the dve expression domain but outside the
wing blade cause the formation of folds around the clone (arrowheads in A-C).
This suggests that elevation of Dve expression in the PW can locally enhance
the proliferation in the surrounding cells. Secondly, with a low frequency, we
find that expression of Dve can non-autonomously induce ectopic expression of
dveP1738-lacZ and nub (see arrow in
A-C). The ectopic Dve-expressing clone (above the arrow in C) is located at
the hinge/notum boundary and expression of both genes is extended towards the
clone. The pseudo-colour image shown in C reveals that the ectopic expression
of Nub occurs in a larger domain than that of Dve, as is the case during
normal development. (D) In a similar manner, we find that the expression of
the inner ring-like domain of wg is correspondingly expanded.
Expression of Wg is shown in red, the clones of Dve expressing cells are shown
in green. The arrow indicates a clone near the inner ring-like expression
domain of Wg. The clone induces an expansion of the inner ring-like expression
domain of Wg in a similar manner to that shown for Nub and
dveP1738-lacZ (see A-C). The third effect caused
by the Dve-expressing clones is highlighted by the asterisks in A and C.
Elevation of Dve expression suppresses the expression of ß-Gal,
suggesting the existence of a negative feedback of Dve on its promoter. This
negative influence of Dve on the activity of its promotor can also be observed
when Dve is expressed with dpp-Gal, as shown in E. (E) Expression of
UAS-dve with dpp-Gal4. Ectopic expression of
dveP1738-lacZ and of Wg is shown in green and
red, respectively. Expression of Dve suppresses the expression of
dveP1738-lacZ (arrow). In addition expression of
wg in the PW is interrupted in the domain of dpp-GAL4. (F,G)
Forced expression of Dve at the DV boundary abolishes the expression of
wg. (F) Expression of Wg. (G) Expression of Wg (blue) and
dveP1738-lacZ (red) in a disc bearing Dve-expressing
clones (green). A comparison of F with G reveals that wg expression
is interrupted (arrows in F) in the Dve-expressing clones. (H) Expression of
UAS-dve with sd-Gal4 abolishes expression of Wg in the wing.
Arrow indicates the wing area, which is poorly developed and does not exhibit
any expression of Wg.