Variation in type two taste receptor genes is associated with bitter tasting phenylthiocarbamide consumption in mature Targhee and Rambouillet rams

Authors: DAVENPORT, KIMBERLY - University Of Idaho; Taylor, Joshua - Bret; HENSLEE, DILLAN - University Of Idaho; SOUTHERLAND, CLAIRE - University Of Idaho; YELICH, JOEL - University Of Idaho; ELLISON, MELINDA - University Of Idaho; MURDOCH, BRENDA - University Of Idaho

Submitted to: Translational Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/4/2021
Publication Date: 9/6/2021
Citation: Davenport, K.M., Taylor, J.B., Henslee, D., Southerland, C., Yelich, J., Ellison, M.J., Murdoch, B.M. 2021. Variation in type two taste receptor genes is associated with bitter tasting phenylthiocarbamide consumption in mature Targhee and Rambouillet rams. Translational Animal Science. 5(3):1-8. https://doi.org/10.1093/tas/txab142.
DOI: https://doi.org/10.1093/tas/txab142

Interpretive Summary: Dietary preference in humans is genetically correlated with the 7-transmembrane G-protein coupled receptors known as type-two taste receptors (TAS2R). These are the only known taste receptors to perceive bitterness. In sheep, bitterness is the most sensitive of the five taste senses, often resulting in the avoidance of some forages. We recently classified male sheep (rams) as those that are very sensitive to bitterness, moderately sensitive to bitterness, and apparently unaware of bitterness in drinking water spiked with phenylthiocarbamide (PTC), a known bittering compound. We then evaluated the relationship between the consumption level of PTC and haplotype of various TAS2R genes. We successfully identified several single nucleotide polymorphisms and haplotypes that were significantly associated with consumption of the bitter tasting PTC compound by the rams. Further research is needed to validate these associations and determine the mechanisms that link genetic variation in TAS2R genes to bitter taste perception in sheep. This may enable producers to select sheep more likely to consume bitter forage such as sagebrush as a flock and rangeland management strategy.

Technical Abstract: Bitter taste perception in sheep can lead to avoidance of specific types of forage, such as sagebrush, which is present on many rangeland grazing systems in the Intermountain West. In humans, bitter taste perception is influenced by genetic variation in several TAS2R genes, including more extensively studied TAS2R38 and TAS2R16. Therefore, the objective of this study was to examine genetic variation in TAS2R genes in relation to consumption of a bitter tasting compound phenylthiocarbamide (PTC) which determines bitter “taster” and “non-taster” status in humans. Rambouillet and Targhee rams (26) were offered various concentrations of PTC solution (0.2 to 12.29 mM) and water in a side-by-side presentation during two experiments. Blood was collected for DNA isolation and sequencing. Nineteen TAS2R genes were amplified and sequenced with long read Oxford Nanopore MinION technology. A total of 1,049 single nucleotide polymorphisms (SNPs) and 26 haplotypes were identified in these genes. Of these, 24 SNPs and 11 haplotypes were significantly associated with PTC consumption in TAS2R3, TAS2R5, TAS2R8, TAS2R9, TAS2R16, TAS2R31-like, TAS2R38, TAS2R39, and TAS2R42-like. Over 50% of the SNPs resulted in a change in amino acid sequence and several resided in potential regulatory regions, which could have downstream functional consequences and influence bitter taste perception in sheep. Further research is needed to validate these associations and elucidate the mechanisms that link genetic variation in TAS2R genes to bitter taste perception in sheep. This may enable producers to select sheep more likely to consume bitter forage such as sagebrush as a flock and rangeland management strategy.