Fig. 8
From: The meaning of ubiquitylation of the DSL ligand Delta for the development of Drosophila
RCI in LqfUIM13E/3A-∆UIM2-GFP wing discs. A, A’ Gbe + Su(H) expression in LqfUIM13E/3A-∆UIM2-GFP wing discs. The arrow points to the residual expression of stripe3. Compare with Fig. 7A, B. B, B’ Detection of RCI in the notal area of wing discs by induction of Dl/Ser-double-mutant clones. Ectopic expression of Gbe + Su(H) is activated in mutant cells at the clone boundary (arrowheads). C–D’’’’ A wing disc bearing lqf- and Dl/Ser mutant clones. The analysed disc is lqf-mutant, rescued by a GFP-tagged lqf construct, expressed under control of the endogenous lqf-promoter. In the rescued discs, the induced Dl/Ser double-mutant clones are labelled by the absence of RFP. The lqf-mutant clones are labelled by absence of the GFP signal caused by the loss of Lqf-GFP. The activity of Notch is revealed by the expression of Gbe + Su(H). The arrowheads highlight regions with strong ectopic induction of Notch activity (Gbe + Su(H) expression) in Dl/Ser-mutant cells at the clone boundary. B–B’’’’’ Independent induction of lqf- and Dl/Ser-clones in discs generates regions devoid of lqf functions adjacent to Dl/Ser-mutant lqf + clones. The clones are outlined in yellow in D’’’, D’’’’. The expected induction of Notch activity (Gbe + Su(H) expression) upon RCI is absent (arrow), indicating that the Dl/Ser expressing cells require the function of lqf. The arrowhead points to a lqf + region adjacent to a Dl/Ser-mutant clone. As expected the Dl/Ser-mutant cells initiate ectopic expression of Gbe + Su(H). The experiment confirms that Lqf is required in the signalling cells to induce Notch activity in the mutant boundary cells. E–F’Dl/Ser-clones in LqfUIM13E/3A-∆UIM2-GFP wing discs. E, E’ Gbe + Su(H) is also activated in the Dl/Ser-double-mutant boundary cells, indicating RCI occurs in cells with a Lqf variant without functional UIMs (arrowheads). Thus, Dl/Ser can signal despite the absence of functional UIMs in Lqf. F, F’ As expected, no induction of Notch activity is observed if the Dl/Ser- mutant clone incudes the whole notum, because no boundary of ligand-expressing and non-expressing-cells are present (asterisk in (F)). G The loss of Dl/Ser-function in LqfUIM13E/3A-∆UIM2-GFP wing discs results in a strong neurogenic phenotype, confirming that the ligands are required for SOP selection in this genetic background