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Type: Journal article
Title: Functional Diversity and Evolution of Bitter Taste Receptors in Egg-Laying Mammals
Author: Itoigawa, A.
Hayakawa, T.
Zhou, Y.
Manning, A.D.
Zhang, G.
Grutzner, F.
Imai, H.
Citation: Molecular Biology and Evolution, 2022; 39(6):msac107-1-msac-9
Publisher: Oxford University Press (OUP)
Issue Date: 2022
ISSN: 0737-4038
Statement of
Akihiro Itoigawa, Takashi Hayakawa, Yang Zhou, Adrian D. Manning, Guojie Zhang, Frank Grutzner, and Hiroo Imai
Abstract: Egg-laying mammals (monotremes) are a sister clade of therians (placental mammals and marsupials) and a key clade to understand mammalian evolution. They are classified into platypus and echidna, which exhibit distinct ecological features such as habitats and diet. Chemosensory genes, which encode sensory receptors for taste and smell, are believed to adapt to the individual habitats and diet of each mammal. In this study, we focused on the molecular evolution of bitter taste receptors (TAS2Rs) in monotremes. The sense of bitter taste is important to detect potentially harmful substances. We comprehensively surveyed agonists of all TAS2Rs in platypus (Ornithorhynchus anatinus) and short-beaked echidna (Tachyglossus aculeatus) and compared their functions with orthologous TAS2Rs of marsupial and placental mammals (i.e., therians). As results, the agonist screening revealed that the deorphanized monotreme receptors were functionally diversified. Platypus TAS2Rs had broader receptive ranges of agonists than those of echidna TAS2Rs. While platypus consumes a variety of aquatic invertebrates, echidna mainly consumes subterranean social insects (ants and termites) as well as other invertebrates. This result indicates that receptive ranges of TAS2Rs could be associated with feeding habits in monotremes. Furthermore, some orthologous receptors in monotremes and therians responded to β-glucosides, which are feeding deterrents in plants and insects. These results suggest that the ability to detect β-glucosides and other substances might be shared and ancestral among mammals.
Keywords: TAS2R
molecular evolution
Rights: © The Author(s) 2022. Published by Oxford University Press on behalf of Society for Molecular Biology and Evolution. This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial License (https://, which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact
DOI: 10.1093/molbev/msac107
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Appears in Collections:Ecology, Evolution and Landscape Science publications

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