Figure 1. Distribution of Hh, Ptc and Smo in the Developing Olfactory System.

(A) The classic Hh signaling pathway. Left, in the absence of Hedgehog (Hh), Patched (Ptc) inhibits Smoothened (Smo) activity. In the absence of Smo activity, Cubitus interruptus (Ci) is processed to a repressor form (Ci^Rep). Right, Hh acts by binding to Ptc and relieving its inhibition of Smo. Active Smo (*) transduces a signal that leads to the maturation of Ci to an activator form (Ci^Act). Among genes activated by Ci^Act is ptc itself.

(B-D) In wild type control late 3^rd instar larval antennal discs, Hh protein is found in the posterior compartment (B). Ptc protein is highly expressed in the anterior-posterior compartment border, expressed at a medium level in the anterior and undetectable in the posterior compartment (C). Smo is ubiquitously expressed, with a slightly higher level in the posterior compartment (D).

(E-G) Antennal discs from late 3^rd instar lavae. Hh protein is greatly diminished in hh^AC/hh^ts2 discs from larvae shifted to restrictive temperature 4 hr before dissection (E). Ptc and Smo proteins are greatly diminished in clones homozygous for ptc^IIW (F) or smo³ (G), respectively. Clone boundaries (blue dashed lines) were determined by loss of the clone marker GFP (see H₁).

(H) Ptc protein is reduced in smo³ clones, shown in magenta with green clone marker (H₁) or alone (H₂). Even in the most anterior part of the anterior compartment, there is a reduction of Ptc protein level in smo³ clones (arrowheads).

A, anterior; P, posterior; D, dorsal; V, ventral. Red dashed lines in (B) and (H₂) mark the precursor of 3^rd segment of antenna (3 AT) and maxillary palp (MP).

(I-J) Cells in the antenna (I) and maxillary palp (J) at 36h after puparium formation (APF) labeled by ptc-Gal4-driven nuclear GFP (green) and hh-nuclear lacZ (magenta). Three single confocal sections at anterior, middle and posterior of the right antenna and maxillary palp are shown. Dorsal (D) is up and lateral (L) is right. Ptc-Gal4 and hh-lacZ label complementary populations of cells that are largely spatially segregated, with some intermingling at the border.

Scale bars, 50 μm (B-H) or 20 μm (I-J). Full genotypes for this and subsequent figures are described in Table S2.

Figure S1 provides additional data on Smo, Ptc, Hh, Ihog and Boi expression in the pupal antenna and maxillary palp, and Smo, Ptc and Ihog proteins in ORN axons.