Identification of markers facilitating the study of support cells in adult olfactory sensilla in Drosophila.

In the Drosophila antenna, olfactory sensilla are the fundamental unit of odor detection and processing. Sensilla house one to four olfactory neurons enwrapped by three distinct support cells: thecogen, trichogen, and tormogen cells. While olfactory neurons and their odor receptors have been extensively studied in Drosophila, and increasingly in other insect species, much less is known about the support cells and their functional roles within the mature sensillar unit. A critical barrier to studying their function has been the lack of validated markers to distinguish and manipulate these cells in adult flies. Here, we systematically identify and characterize tools to differentially label specific olfactory support cells in the antenna, including svT2A-GAL4 as a broad support cell marker. First, we confirm that ASE5-GAL4 labels olfactory tormogen cells, which are also strongly labeled by an anti-Su(H) antibody. Next, we demonstrate that a prospero antibody broadly and exclusively marks thecogen cells, unlike the previously used marker nompA-GAL4. The pros-positive cells are also labeled by a recently developed prosT2A-GAL4 line, but surprisingly, they are distinct from those labeled by a widely used pros-GAL4 line, which instead labels olfactory neurons. Third, we generate and validate the first reporter line for olfactory trichogen cells, atkGAL4. Finally, we provide evidence that each tool may function similarly in the maxillary palp. Together, our findings create a framework for distinguishing olfactory support cell classes in the adult fly antenna, a crucial step towards understanding their individual contributions to sensillar function.