Fig. 3. sens and da are required for AWM mechanosensory and PWM bristle formation. (A) A MARCM clone of Df(1)260-1 in the AWM. The mutant bristles are yellow and singed. (B,B') A MARCM clone of Df(1)260-1 in the wing of an 8- to 10-hour APF pupa stained for Sens (red) and Atonal (green). CD8-GFP (blue) marks the membranes of the mutant cells. Note that the accumulation of Sens in mechanosensory pIs is not affected by the loss of the ASC. However, despite the background staining of Ato along the physical margin due to the high gain used in the scans, no Ato staining is detected in mechanosensory pIs. (C,D) AWM (C) and PWM (D) bristles are lost in sens clones. The mutant tissue in C is marked with multiple wing hairs (mwh). Note that upon loss of stout bristles, a chemosensory bristle (arrow) is misplaced to the stout row, as reported previously (Couso et al., 1994). (E,F) da³ clones lack AWM (E) and PWM (F) bristles. The mutant tissues are marked by crinkled. (G-I') sens expression is activated by Wingless in the WM. All panels show the central part of the wing pouch in third instar wing imaginal discs. Arrows point to the WM; the dashed line depicts the anteroposterior (AP) boundary of the wing disc; anterior to the left. (G) Sens expression in a y w (wild type) wing disc. (H,H') Loss of Wg (green) and Sens (red) expression in a wg^CX4 clone. The mutant tissue lacks GFP (blue). Note that even in the heterozygous tissue flanking the mutant clone, Sens expression is decreased, indicating that sens requires very high levels of Wingless signaling for proper expression. (I,I') Overexpression of Wg-GFP (green) along the AP boundary induces Sens (red) expression.