Fig. 2. DE-cadherin promotes rotation. (A,B) Tangential sections of adult eyes (dorsal is upwards, anterior leftwards) with a schematic representation shown in bottom panels (arrows as in Fig. 1). (A) Eye of homozygous hypomorphic shg^R6 escaper, showing rotation defects with ommatidia often rotating less than 90°. (B) Clone of an intermediate allele, shg^P34-1 (marked by increased pigment levels; grey area in schematic) show rotation defects in addition to severe adhesion defects causing photoreceptor cell loss. (C-F) Confocal microscopy images of ventral regions of 3rd instar eye discs (anterior is leftwards, dorsal upwards). (C-C'') Clones of intermediate shg^P34-1 allele. Blue: Elav, all photoreceptors. Red: Bar, labeling R1/R6 and highlighting rotation angle of each cluster. Green: GFP labeling wild-type tissue, mutant clones marked by absence of GFP. Non-rotating ommatidia are present, as visualized by Bar-staining (red in C,C') in mutant areas. (C'') Semi-schematic version of C', white bars indicate orientation of wild type and yellow bars indicate orientation of mutant clusters. (D-D'') Clones of shg^P34-1 allele. Rotation is abnormal from its onset: anti-Spalt (Sal in red) is the earliest R3/R4 marker. R3/R4 fate is correctly specified in shg^P34-1 clone, but many ommatidia do not initiate rotation (Elav, blue; GFP, green, marking wild-type tissue). White and yellow bars in D'' are as in C'' (white representing wild-type and yellow mutant clusters). (D',D'') Orange arrowheads mark preclusters composed of wild-type cells adjacent to mutant tissue that are misrotated, suggesting that shg/DE-cad is also required in interommatidial cells for rotation. (E-E') sev>DEcad^WT partially rescues rotation in shg^P34-1 clones (Bar, red; GFP, green, marking wild-type tissue). Many mutant preclusters have a `rescued' rotation angle. (F,F') Markers of apicobasal polarity are normally localized within shg^P34-1 clones. Discs Large (Dlg; red), apical F-actin (phalloidin, green) and GFP (blue; marking wild-type tissue) are shown. Apical to epithelial disc layer are the squamous cells of the peripodial membrane (yellow arrowhead).