en |
Smallest bitter taste receptor (T2Rs) gene repertoire in carnivores
HU, Ling-Ling & SHI, Peng
Abstract
Bitter taste reception is presumably associated with dietary selection, preventing animals from ingesting potentially
harmful compounds. Accordingly, carnivores, who encounter these toxic substances less often, should have fewer genes associated
with bitter taste reception compared with herbivores and omnivores. To investigate the genetic basis of bitter taste reception, we
confirmed bitter taste receptor (T2R) genes previously found in the genome sequences of two herbivores (cow and horse), two
omnivores (mouse and rat) and one carnivore (dog). We also identified, for the first time, the T2R repertoire from the genome of
other four carnivore species (ferret, giant panda, polar bear and cat) and detected 17−20 bitter receptor genes from the five carnivore
genomes, including 12−16 intact genes, 0−1 partial but putatively functional genes, and 3−8 pseudogenes. Both the intact T2R genes
and the total T2R gene number among carnivores were the smallest among the tested species, supporting earlier speculations that
carnivores have fewer T2R genes, herbivores an intermediate number, and omnivores the largest T2R gene repertoire. To further
explain the genetic basis for this disparity, we constructed a phylogenetic tree, which showed most of the T2R genes from the five
carnivores were one-to-one orthologs across the tree, suggesting that carnivore T2Rs were conserved among mammals. Similarly, the
small carnivore T2R family size was likely due to rare duplication events. Collectively, these results strengthen arguments for the
connection between T2R gene family size, diet and habit.
Keywords
T2R; Bitter taste; Carnivores; Duplication
|