Figure 3. A topological map of IR expression in the antenna.
(A) Left: cartoons of the Drosophila antenna, in which sensory structures are color-coded by their developmental specification by the proneural genes amos (blue) or atonal (red). Right: two-color RNA in situ hybridization for OR83b (magenta) and either OR35a (green, left), IR64a (green, middle) or IR76b (green, right) on antennal sections of wildtype (top), amos mutant (amos1/Df(2L)M36F-S6) (middle) and atonal mutant (ato1/Df(3R)p13) (bottom) animals. Scale bar for all panels is 20 μm.
(B) Two-color RNA in situ hybridization for IR76b (green) and the neuronal marker elav (magenta) on an antennal section of a wildtype antenna. Scale bar is 20 μm.
(C) Two-color RNA in situ hybridization on an antennal section for IR8a (green) and IR25a (magenta). Scale bar is 20 μm.
(D) One-color RNA in situ hybridization on antennal sections reveals expression of IR21a in the arista.
(E) One- and two-color RNA in situ hybridization on antennal sections reveals co-expression of IR40a (green) and IR93a (magenta) in neurons surrounding the first and second chamber of the sacculus (top) and expression of IR64a (middle) and IR21a (bottom) in neurons surrounding the third chamber of the sacculus. Scale bars are 10 μm.
(F) Two- and three-color RNA in situ hybridization for the indicated combinations of IR genes expressed in neurons in the main portion of the antenna. Pairwise comparison of physically adjacent neurons allows the definition of four distinct clusters (A-D) of IR-expressing neurons, summarized in the schemes on the left. IR genes expressed in more than one cluster are highlighted in color. The parentheses around IR75c refer to the expression of this gene in only a subset of cluster C (111 IR75c-expressing cells/155 IR75b-expressing cells =71.6%). Scale bar for all two-color panels is 20 μm, and for all three-color panels is 5 μm.