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Description
Insects utilize their antennal olfactory system to detect numerous environmental odors to aid in behaviors such as identifying food sources, host seeking, and mating. While Olfactory Receptor Neurons (ORNs) have been extensively studied, much less is known about the tormogen, trichogen, and thecogen support cells that are co-housed in olfactory sensilla. The Drosophila melanogaster antennal transcriptome contains many putative Odorant Degrading Enzymes (ODEs), and support cells are thought to use these to metabolize odors. One abundant class of antennal ODEs is the Cytochrome P450 (Cyp) gene superfamily. However, their cellular localization and potential contribution to odorant responses is poorly understood. Here, we investigated the localization of thirteen antennal Cyps, including those most highly expressed and those with antennal-enriched expression compared to other tissues. Using newly generated transgenic LexA reporter lines, we found that most Cyps are broadly expressed across the antenna, whereas a few have more restricted expression. While expression of a few Cyps may be limited to the antenna, many are additionally expressed in the maxillary palp or the Johnston’s organ. Further localization of one narrowly-expressed Cyp, Cyp313a4, revealed that it is exclusively expressed in two subtypes of coeloconic sensilla, suggesting it may contribute specifically to their olfactory function. The expression of Cyps in different antennal cell types was investigated using markers for neurons (anti-elav), thecogen cells (anti-pros), trichogen cells (atk-Gal4), tormogen cells (ASE5-Gal4), and epithelial cells (Obp19d-Gal4). Among support cells, Cyps were predominantly expressed by trichogen cells, with some expression in tormogen cells and rarely thecogen cells. Unusually, Cyp313a1 is mostly expressed by a subset of olfactory neurons; no other Cyps have neuronal expression. In addition to support cell expression, many Cyps are also expressed by epithelial cells. Together, this work presents the first map of Cyp expression in the Drosophila antenna and can serve as a roadmap for future studies on their functional roles.
