International collaborative research teams such as Hokkaido University, Meiji University, Kyoto University, Adelaide University, Australian National University, and Copenhagen University have a bitter taste of "egg-laying mammals" (single-holes), which have only two groups in the world, Kamonohashi and Harimogra. Was analyzed.
It is estimated that embryonic mammals, including humans, and platypus and echidna monotremes diverged 1 million years ago (Jurassic).The study of monotremes, which are members of mammals but still retain the characteristic of their ancestors of "laying eggs", has important implications for clarifying the evolution of mammals.
Therefore, this research team focused on the taste of monotremes, and investigated the "bitter taste" related to the selection of edible substances by detecting harmful substances such as poisons.As a result, although the platypus has only 7 types of bitter taste receptors (26 types in humans), it contains a universal bitter taste receptor that can detect various bitter taste substances at once. It was found that 24 of the 18 types of bitterness substances used in the above can be detected.On the other hand, echidna had only three bitter taste receptors and lost the universal bitter taste receptor of platypus, and it was found that the number of detectable bitter taste substances was small.
From this result, the platypus, which is semi-aquatic and eats various organisms in the water, uses the bitterness sensation for proper food selection, while the terrestrial ant and termite-specific eating echidna has the importance of bitterness. It is said that it may have dropped and only a limited bitterness may have been felt.
It was also found that most of the monotreme bitter taste receptors are closely related to the bitter taste receptor TAS2R16 of embryonic mammals, and these commonly detect toxic glycosides contained in plants as bitter taste.In other words, it can be seen that the ability to feel bitter phytotoxicity played a certain role before the divergence of monotremes and embryonic mammals, and was maintained until this world.
Based on this research, it is expected that the evolution of the taste function of monotremes and its ecological significance will be further elucidated.
Paper information:[Molecular Biology and Evolution] Functional diversity and evolution of bitter taste receptors in egg-laying mammals
