Figure 2. Hh Signaling Is Required for Axon Targeting of a Subset of ORN Classes.

(A) Schematic of antennae illustrating mosaic analysis. Cell bodies of a given OR class are shown. ey-FLP may create large clones that cover up to 50% of cells in the antennal disc, whereas hs-FLP generates small clones. In both cases only ORNs of a given class are labeled because of the use of Or-Gal4 and MARCM.

(B) Examples of ORN axon targeting defects (arrowheads) in ey-FLP induced smo³ and ihog clones, and in hs-FLP induced smo³ and ptc^IIW clones. Or23a axons target normally in smo³ and ihog mutants but exhibit targeting defects in ptc^IIW mutant (arrowhead), whereas Or43a and 59c axons exhibit targeting defects in smo³ and ihog mutants (arrowheads) but normal targeting in ptc^IIW mutant clones. Positions of Or-Gal4 labeled cells remain unchanged in the antenna and maxillary palp in ey-FLP induced smo³ or ihog mutant clones (data not shown). Glomeruli are labeled by nc82 (magenta) and ORN axons by Or-Gal4-driven mCD8GFP (green). In control, Or59c-Gal4 is expressed in Or59c ORNs targeting to glomerulus 1 (yellow arrows) and ectopically expressed in ORNs that target to glomerulus VM7 (white arrows). Since VM7 targeting is normal in smo mutant as revealed by Or42a-Gal4 (Table 1), targeting defects in Or59c-Gal4 labeled ORNs originate from Or59c ORNs. In control, Or23a-Gal4 is expressed in Or23a ORNs targeting to glomerulus DA3 (yellow arrows) and ectopically expressed in ORNs that target to glomerulus DC3 (white arrows). Since DC3 targeting is normal in ptc mutant as revealed by Or83c-Gal4 (Table 1), targeting defects in Or23a-Gal4 labeled ORNs originate from Or23a ORNs (see also Figure S2B). Scale bar, 20 μm.

Table S1 provide more examples of axon targeting in other ORN classes.

Figure S2 provides examples to illustrate several criteria for phenotypic scoring.