Generation of Odorant Receptor-QF2 Knock-In Drivers for Improved Analysis of Olfactory Circuits in Drosophila.

Drosophila melanogaster has provided numerous insights into the olfactory system, primarily relying on a series of transgenic Gal4 drivers. The combined use of Gal4/UAS and a second binary expression system, such as the QF/QUAS system, provides the opportunity to manipulate the two distinct cell populations, thereby accelerating the elucidation of the olfactory neural mechanisms. However, resources apart from the Gal4/UAS system have been poorly developed. In this study, we generated a series of odorant receptor (Or)-QF2 knock-in driver (Or-QF2(KI)) lines for 23 Ors using the CRISPR/Cas9 knock-in method. In these lines, the QF2 protein is cotranslated with each Or product. The expression pattern of the Or-QF2(KI) drivers mostly corresponded to that of the Or-Gal4 drivers. In addition, the Or42a-QF2(KI) driver identified the additional expression pattern of Or42a, which is consistent with the data of single-nucleus RNA sequencing and is attributed to the Or-QF2(KI) drivers' ability to reflect the endogenous expression of the Or genes. Thus, these Or-QF2(KI) drivers can be used as valuable genetic tools for olfactory research in Drosophila.