A team of researchers from the University of Cologne, collaborating with colleagues from the Leibniz Institute for Food Systems Biology in Freising, has made a fascinating discovery about the taste perception of sharks and rays, which are cartilaginous fish. They identified a receptor for bitter taste in twelve different cartilaginous fish, challenging the previous belief that such taste receptors only existed in bony vertebrates, like humans.
The taste receptor in question is part of the taste receptors type 2 (T2R), responsible for how humans perceive bitter and potentially toxic foods. The study, titled ‘A singular shark bitter taste receptor provides insights into the evolution of bitter taste perception,’ was published in the journal Proceedings of the National Academy of Sciences (PNAS).
In the past, studying sharks at the molecular level was challenging due to their relatively large genomes, making sequencing complex and time-consuming. However, advancements in sequencing technologies have allowed researchers to explore gene sequences in cartilaginous fishes more effectively.
The team, led by Dr. Maik Behrens, Tatjana Lang, and Professor Dr. Sigrun Korsching, used advanced techniques to search for bitter taste receptors specifically in cartilaginous fish. Out of seventeen cartilaginous fish genomes studied, twelve contained genes for the taste receptors type 2, and each species had only one T2R gene, named T2R1.
The discovery of a single T2R gene suggests it is the original form of these bitter taste receptors, without alterations through gene duplication and subsequent specialization. This finding provides valuable insights into the evolution of these receptors, dating back almost 500 million years to the last common ancestor of cartilaginous and bony fish.
The researchers introduced the T2R1 gene of bamboo sharks and catsharks into cell lines. The results showed that both shark species could taste bitter substances perceived by humans, such as colchicine or bile acid. Screening ninety-four human bitter substances identified eleven that could activate the sharks’ receptors. Some of these substances also activated the bitter taste receptors of the coelacanth, an ancient bony fish species.
Professor Sigrun Korsching expressed amazement at the conservation of this function throughout the evolution of vertebrates. The study sheds light on the molecular and functional origins of an entire family of bitter taste receptors, providing a deeper understanding of taste perception across different species.
