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Fig. 4. Kul is required for unidirectional Notch signaling in the pupal wing.
Expression of Dl in the wing veins was followed by anti-Dl (red), while the
activation of Notch signaling was monitored by anti-ß-Gal staining of the
Su(H)m8-lacZ reporter (blue). The L4
vein is indicated by an arrowhead. (A,C) In wild-type wings, Dl is expressed
in 2-3 cell rows, marking the future veins.
Su(H)m8 is excluded from the veins and is induced
in up to five cell rows adjacent to the vein on each side. (B,D) In wings
expressing ds-kul in the sal domain, dramatic alterations in
both patterns were observed. Dl is expanded beyond the normal vein region
(asterisk). Consequently, the cells expressing ectopic Dl trigger activation
of Notch signaling within the vein (arrow). In some regions, expression of Dl
is eliminated in the vein (arrowhead), possibly as a result of ectopic Notch
signaling. (E) Scheme: in wild-type wings, Dl is expressed by the vein cells,
activating Notch in the adjacent cells to induce an inter-vein fate within the
pro-vein territory. Following Kul overexpression, the levels of Dl are reduced
and Notch signaling is compromised, leading to an expansion of vein cell fate
within the pro-vein territory (Fig.
2C). By contrast, when ds-kul is expressed, the levels of
Dl rise in the cells adjacent to the veins, leading to Notch activation within
the vein, and to the ectopic induction of an inter-vein fate
(Fig. 2B and
Fig. 4B,D).
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