Characterization of Drosophila olfactory sensory neuron performance

Insects’ sense of smell plays a crucial role in detecting and distinguishing array of volatile chemical compounds that are present in the environment. They detect such volatile chemical compounds with great sensitivity and efficiency with the help of their olfactory sensory organs- the antenna and the maxillary palp. On the third antennal segment, different types of sensilla are present that may house one to four olfactory sensory neurons (OSNs). On the OSN dendrites, different classes of chemosensory receptor proteins are expressed. Our study focuses only on one class of chemosensory receptor protein called odorant receptors (ORs). ORs form a heteromeric complex composed of odor-specific proteins OrX and a ubiquitous co-receptor protein Orco. They function as odor-gated non-selective cation ion channels that allows the passage of Ca2+ ions into the OSNs. This thesis aims to examine the function and regulation of Drosophila melanogaster ORs. As ORs play a crucial role in olfactory signal transduction mechanisms. It is worth developing novel tools and techniques by which we can improve our current understanding on insect olfaction. To explore this, in manuscript 1, we studied how a single point mutation (lysine to asparagine) in the Orco Calmodulin CaM binding site (CBS) (OrcoK339N) affects both OR function and the olfactory behavior of the flies. In manuscript 2, we developed an in vivo method to excite D. melanogaster ORs with airborne odors. In addition to this, we also established a method to isolate D. melanogaster OSNs and introduced a new embedding technique to fix these OSNs and perform functional imaging on these OSNs. In last manuscript, we developed a D. melanogaster fly that expresses GFP at the N-terminal region of Orco (N-GFP-Orco) in the orco null mutant background and investigated if GFP insertion would affect the olfactory capability of the fly. This fly was designed as tool to visualize membrane-tagged OR proteins and use it for our future studies.