The ability to taste is a crucial sense that allows us to distinguish between beneficial and harmful foods. Our preference for sweet and savory flavors is rooted in our need to consume carbohydrates and proteins. Understanding the origins and evolution of taste receptors is essential in unraveling the feeding behavior of organisms and piecing together the history of life on Earth.
Umami, commonly known as the savory taste, is one of the important tastes in our palate. It is associated with proteins, which are essential in the diets of many organisms. Taste receptor type 1 (T1R) is responsible for detecting both sweet and umami tastes in mammals. The TAS1R family of genes, including TAS1R1, TAS1R2, and TAS1R3, encode this taste receptor, which traces back to a common ancestor of bony vertebrates.
However, the gene pattern observed in coelacanth and cartilaginous fishes deviates from this sequence. Researchers have identified taxonomically unplaced TAS1R genes in these fishes, suggesting that the evolutionary history of taste receptors is not fully understood.
In a groundbreaking study published in Nature Ecology & Evolution on December 13, 2023, a research team led by Associate Professor Hidenori Nishihara from Kindai University and Professor Yoshiro Ishimaru from Meiji University, Japan, has identified five new groups within the TAS1R family. This discovery is the result of a genome-wide survey of jawed vertebrates, including all major fish groups.
The study also involved the contributions of Senior Assistant Professor Yasuka Toda from Meiji University, Professor Masataka Okabe from The Jikei University School of Medicine, Professor Shigehiro Kuraku from the National Institute of Genetics, and Project Associate Professor Shinji Okada from The University of Tokyo.
The researchers discovered that the vertebrate ancestor possessed a larger number of T1Rs compared to most modern vertebrates. This finding challenges the conventional belief that only three T1R family members were retained during the course of evolution. The researchers named the newly discovered taste receptor genes TAS1R4, TAS1R5, TAS1R6, TAS1R7, and TAS1R8 based on their distribution among species with a common ancestor. TAS1R4 genes were found in lizards, axolotl, lungfishes, coelacanth, bichir, and cartilaginous fishes, but were absent in mammals, birds, crocodilians, turtles, and teleost fishes. Axolotl, lungfishes, and coelacanth were found to possess TAS1R5 exclusively.
The research team found a close evolutionary relationship between TAS1R5, TAS1R1, and TAS1R2, indicating a shared ancestry among these genes. Cartilaginous fishes were discovered to exclusively possess TAS1R6, which evolved from the same ancestral gene that led to TAS1R1, TAS1R2, and TAS1R5. Axolotl and lizards were found to possess TAS1R7, while bichir and lungfishes possessed TAS1R8. The researchers deduced that these two genes originated in the common ancestor of jawed vertebrates.
The study also revealed diversity in the existing TAS1R genes. For example, TAS1R3 of bony vertebrates was found to be divided into TAS1R3A and TAS1R3B. TAS1R3A was present in tetrapods and lungfishes, whereas TAS1R3B was identified in amphibians, lungfishes, coelacanths, and ray-finned fishes. Additionally, TAS1R2 was found to have diversified into TAS1R2A and TAS1R2B, challenging the traditional notion that TAS1R2 forms a single gene group.
“These findings make it easier for us to deduce the taste preferences of diverse vertebrates. This, in turn, can have potential applications such as the development of pet foods and attractants tailored to the preferences of fish, amphibians, and reptiles,” explains Prof. Nishihara.
The study’s findings not only shed light on the evolutionary history of taste receptors but also have practical implications. They pave the way for a better understanding of taste preferences among different vertebrates and open doors for the development of specialized pet foods and attractants. Through these applications, researchers can cater to the specific tastes of fish, amphibians, and reptiles, offering new possibilities in the field of nutrition and animal care.
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Source: Coherent Market Insights, Public sources, Desk research
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