Comparative genomics of the sheep Tas2r repertoire to cattle, goat, human, dog, and mice

Type two taste receptors (Tas2r) are the only taste receptors that distinguish bitter-tasting compounds. Human Tas2r genes have been extensively studied and have been associated with dietary preferences, health, substance dependence, and other diseases. Sheep are an important livestock species known for grazing vast rangelands with variable ecology and plant communities. However, the limited work related to Tas2r gene repertoires in the reference genomes of grazing animals creates a challenge for understanding how these genes influence diet selection preferences. Tas2r genes typically cluster on two regions of the genome. In the second cluster of the sheep (OAR_rambouillet_1.0), goat (ARS1), and cattle (ARS-UCD1.2) reference genomes, there are six, nine, and two Tas2r genes that were not annotated, respectively. Comparative genomic strategies were used to cross-reference sheep Tas2r genes in cattle, goat, human, dog, and mice for the proposed annotations. A nucleotide similarity comparison of the whole Tas2r repertoires for the three grazing species suggested that goat and cattle are similar to sheep (≥ 95.5% and ≥ 91.9% similarity, respectively). Several Tas2r genes found in sheep, cattle, and goat are likely not found in human, dog, or mice and may be reserved to ruminants or animals of similar feeding ecology. Using a comparative genomics approach, this paper proposes annotations for sheep, cattle, and goat Tas2r genes. Further research is needed to better understand how Tas2r genes may influence diet selection in grazing ruminant species, which could provide more insight into management of western rangelands through grazing strategies.