Insects perceive countless odors with the help of odorant receptors (ORs) expressed by olfactory sensory neurons (OSNs) located in antenna and maxillary palps. OR complexes are composed of odor specific proteins OrX and olfactory co-receptor proteins Orco, both with extracellular C-terminus and intracellular N-terminus. In this study, we generated a genetically modified Drosophila melanogaster fly line that expresses green fluorescent protein (GFP) at the Orco N-terminus (UAS-N-GFP-ORCO) in Orco null mutant background (Orco1) using GAL4-UAS system. We first obtained four phenotypes for which we performed cryosectioning and immunolabeling in the antenna. In preliminary observations, we see that these fly lines have differences in OR expression patterns. Therefore we investigate the differences in fluorescence intensities from stomata and outer dendrites from the antennal cross sections. We also tested the olfactory capability of these flies using single sensillum recording (SSR). We could show that olfaction was not impaired by GFP insertion. As Orco guides OR trafficking to the OSN dendrites, we check whether insertion of GFP at the Orco N-terminus affects the trafficking. Further we want to use this transgenic fly line to resolve the structure of OR complexes using Cryo electron microscopy (cryo-EM).