Fig. 3.

Xath5 induces fly R8 formation but Math5 does so rarely. Drosophila imaginal discs double labeled with anti-Boss (green) to mark R8 photoreceptor cells and anti-Elav (red) to mark differentiated photoreceptor neurons. In each panel, a horizontal arrow marks the position of morphogenetic furrow (MF) and anterior is down. (A) w-; gal4-7, ato¹/TM6Tb control. Elav expression highlights normal ommatidial patterning. One R8 cell expressing Boss (green punctate staining) is present within each ommatidium posterior to the MF. (B) As reported by Sun et al. (2000), atonal induces extra R8 cells (vertical arrows) and ommatidial patterning is slightly disorganized. (C) Xath5 induces R8 cell formation. Ommatidial patterning is similar to atonal rescues (compare B and C). (D) Math5 induces very few ommatidia, and these are always located within a small posterior patch of the imaginal disc. Vertical arrows point to two ommatidia with Boss expression (in green). (E) Infrequent induction of R8-containing ommatidia (vertical arrows) by UAS-scute. (F) UAS-NeuroD rescued eye discs with R8 cells, as in UAS-Xath5 (compare F and C). Scale bar, 25 μm.