Atypical Membrane Topology and Heteromeric Function of Drosophila Odorant Receptors In Vivo
(A) The Drosophila olfactory system. Left panel: false-colored scanning electron micrograph image of a Drosophila head illustrating the major olfactory (antenna) and gustatory (proboscis) organs (photo: Jürgen Berger, Max Planck Institute for Developmental Biology, Tübingen, Germany). Center panel: schematic of olfactory sensilla distribution on the third antennal segment. Right panel: schematic of OSN anatomy.
(B) Immunostaining for OR83b (green) and OR22a/b (red) in antennal sections of a wild-type (yw) animal. Arrowheads mark enrichment of perinuclear OR83b that co-localize with the trace amount of OR22a/b present in the cell body.
(C) Immunostaining for OR22a/b (red) and mCD8:GFP (α-GFP, green) in antennal sections of control heterozygous (Or83b1/+, top row) and homozygous (Or83b1/Or83b2, bottom row) Or83b null-mutant animals. The position of the field of view, in this and subsequent figures, is illustrated by the blue square in the antennal schematic (inset in upper left panel). Images of control and mutant samples were taken at identical confocal settings to permit comparison of signal intensities. Therefore, levels of OR22a/b are lower in (C) than in (D and E), in which confocal settings have been adjusted to permit visualization of OR22a/b in Or83b mutants.
(D) Immunostaining for OR22a/b (red) and Golgi (α-Golgi, green) in antennal sections of control heterozygous (top panel) and homozygous (bottom panel) Or83b null-mutant animals.
(E) Immunostaining for OR22a/b (red) and ER (α-KDEL, green) in antennal sections of heterozygous control (top panel) and homozygous (bottom panel) Or83b null-mutant animals. Mislocalized OR22a/b and KDEL accumulations overlap in the mutant (arrowheads in lower left panel). Autofluorescence of the antennal cuticle is visible in the green channel at the base of the sensilla. In (D and E), confocal settings of the red channel were adjusted to permit clear visualization of the weaker OR22a/b signal in Or83b mutants.