Fig. 4. Robo/Slit-dependent signaling regulates glomerular patterning. Orientation is as described for previous figures. (A-F).The SG18.1-Gal4 UAS-GFP recombinant line was used to visualize sensory neuron within the lobe and also to misexpress genes under UAS control. (A) SG18.1-Gal4 UAS-GFP/UAS-robo;UAS-robo(2X)/+ (three copies). Glomerular formation is abrogated but the commissure is still present (arrow). (B) SG18.1-Gal4 UAS-GFP/UAS-robo3. Positions of most terminals are shifted to the dorsomedial location within the lobe (indicated with broken red lines). Commissure is unaffected (arrow) (C) SG18.1-Gal4 UAS-GFP/UAS-robo2.? indicates the position of the commissure that is absent. (D) SG18.1 UAS-GFP UAS-robo2/Df(2R) WMG (Df(2R)Slit). Commissure (arrow) formation is restored when dose of the Slit ligand is reduced by half. Glomerular morphology is also restored (asterisks). (E) SG18.1 UAS-GFP UAS-robo2/UAS-comm: partial restoration of glomerular morphology (^*) and complete rescue of the commissure (arrow). (F) SG18.1 UAS-GFP UAS-robo2/UAS-Dcdc^v12. The commissure is present but sensory axons are much more loosely packed than in the normal (arrows). (G-I) Adult olfactory lobes stained with the synaptic marker mAbnc82. (G) Normal controls. (H,I) loco-Gal4/UAS-Slit: ectopic glomeruli are circled by broken red lines. Only a few glomeruli are recognizable when Slit is ectopically expressed (marked by an asterisk).