Browsing by Subject "chemosensation"

Gustation, also known as taste perception, is critical for the survival of most animal species. The fruit fly Drosophila melanogaster employs 68 different gustatory receptors (GRs) for the detection of sugars, bitter or toxic compounds, and pheromones. However, with a few notable exceptions, the functions of most GRs involved in feeding are unknown. Our research has focused on a cluster of highly-related Drosophila Grs, known as the Gr64 family, that have been shown to be critical for the perception of multiple sugars. Furthermore, we have demonstrated that another gene related to the Gr64 genes, Gr61a, is a sugar receptor that is narrowly tuned to a subset of pyranose sugars and may (along with the Gr64 genes) be indispensable for early fly development.

As a complementary approach to our behavioral analysis, we have examined the expression pattern of the Drosophila sugar receptors using knock-in driver alleles created by homologous recombination. As expected, most of these drivers have shown strong expression in various taste tissues. Intriguingly, some of these knock-in alleles also show expression in the maxillary palp and antenna, tissues previously thought to be involved only in olfaction. These expression patterns raise interesting questions about the true range of function of these chemosensory receptors and whether or not they might be involved in olfaction as well as gustation.

Deciphering natural odor plumes with dynamic changes in odor concentrations presents a common challenge to all animals. A fundamental challenge in studying the organization principles of the olfactory system to encode odor concentration information is the lack of comprehensively identified sets of activated odorant receptors (ORs) across an odorant concentration range inside freely behaving animals. In mammals, this has recently become feasible with high-throughput sequencing-based methods that identify populations of odorant activated ORs in vivo. In this study, we characterized the mouse OR repertoires activated by two odorants, acetophenone (ACT) and 2,5-dihydro-2,4,5-trimethylthiazoline (TMT), from 0.01% to 100% (v/v) concentrations. We also investigated the OR repertoires for structural derivatives of TMT (component of fox odor) such as 2­methyl-2-thiazoline (2MT) and 2,4,5-Trimethylthiazole (nTMT) and 2-sec-butyl-4,5-dihydrothiazole (SBT) for 1% and 100% (v/v) concentrations. We used a combination of in vivo, in situ and in silico approaches to investigate ORs with distinct sensitivities to the tested odorants. We examined Olfr923, which we identified to be one of the most sensitive ACT ORs based on our pS6-IP-Seq data. Using a mouse line that genetically labels Olfr923 positive axons, we provide evidence that ACT activates the Olfr923 glomerulus in the olfactory bulb. This study sheds light on the active process in which unique OR repertoires may collectively facilitate the discrimination of odorant concentrations. Together, these odorant receptors may shape the dynamic aspects of olfactory sensitivity and facilitate odorant intensity coding.