Fig. 1. The dgo eye phenotype. (A) Schematic drawing of 3rd instar larval eye imaginal disc, with the morphogenetic furrow (MF; yellow) and the DV midline (the equator; gray) indicated. Anterior is leftwards and dorsal upwards in this and all subsequent figures. Initially, ommatidial preclusters are symmetrical and organized in the AP axis. Subsequently, they rotate 90° with respect to the equator; at the end of this process chirality is established by the positions of R3 and R4. (Right) Schematic presentation of chiral organization of dorsal and ventral adult ommatidia; in addition to the chiral forms, symmetrical clusters with R3/R3 or R4/R4 cell pairs as found in PCP mutants are shown. R3 cells are highlighted in green and R4s in magenta. (B) Partial view of a developing eye imaginal disc demonstrating the regularity of polarity establishment. Ommatidial clusters are marked with anti-Elav (green; labeling all photoreceptors) and svp-lacZ [magenta: svp is expressed initially in R3/R4 (see left side of panel) and later also in R1/R6 at weaker levels]. The MF is on left side adjacent to field shown. Orientation of some dorsal ommatidial preclusters is highlighted with yellow arrows; white line marks the equator. (C,D) Tangential sections of adult eyes with the respective schematic presentations of the genotypes indicated. Wild-type dorsal and ventral ommatidial arrangement is represented by black and red arrows, respectively; symmetrical R3/R3 and R4/R4 ommatidia are represented by green and magenta arrows, respectively. (C) Wild-type eye with regular arrangement of dorsal and ventral ommatidia around equator. (D) dgo³⁸⁰ eye (null allele). The equatorial arrangement is disturbed with a random arrangement of both chiralities (black and red arrows), and the presence of many symmetrical clusters of both R3/R3 and R4/R4 types (green and magenta arrows). (E,E') Confocal microscopy images of mosaic 3rd instar eye disc, with dgo^– tissue marked by absence of green (GFP); anti-Bar labeling R1/R6 (magenta) highlights orientation of clusters. (E') Single channel showing Bar staining. Orientation defects of the preclusters are visible from early stages in mutant tissue. Examples with abnormal orientation are indicated with white arrows; yellow arrows indicate wild-type orientation for comparison.