(A) Diagram of a generic sensillum containing ORNs, thecogen cells labeled with nompA-GAL4, trichogen cells (Tr), and tormogen cells labeled with ASE5-GAL4, separated from neighboring sensilla by epidermal (E) cells. Adapted from (Steinbrecht et al., 1992). (B–D), (F–J) Confocal images of antennal sections labeled with Obp antisense probes (red) and an antibody against GFP (green) driven by the thecogen cell driver nompA-GAL4 (B,D,F), and the tormogen cell driver ASE5-GAL4 (C–D,G–J). Yellow indicates coexpression. (E) Summary of coexpression experiments. The dark, solid red rectangle indicates that Obp84a was co-expressed with the thecogen cell type marker sensilla consistently in those sensilla that express Obp84a. In many cases, indicated by light, stippled red rectangles, an Obp was co-expressed in a specific cell type in some but not all sensilla. An empty rectangle indicates that the Obp did not co-localize with that cell type marker in any sensilla examined. F,G Images of whole antennal sections. Obp83a is expressed in many cells that are not labeled by the thecogen (F) or tormogen cell driver (G). (H) Two trichoid sensilla that each house one tormogen cell (green) and two Obp83b-expressing cells (red). (I) Obp19a is coexpressed with the tormogen cell driver in one sensillum. The image shows the same cell as in (C) but in a different focal plane. (J) Obp19a is not coexpressed with the tormogen cell driver in another sensillum. Scale bars = 2 μm.