Xiang Ling, Chen Yanhong, Jing Haohao, Li Yingcan, Huang Chen, Lu Qin, Zhao Huabin
Key Laboratory of Biodiversity and Environment on the Qinghai-Tibetan Plateau, Ministry of Education, School of Ecology and Environment, Tibet University, Lhasa 850000, China.
State Key Laboratory of Virology and Biosafety, Hubei Key Laboratory of Cell Homeostasis, Frontier Science Center for Immunology and Metabolism, College of Life Sciences, Wuhan University, Wuhan 430072, China.
Mol Biol Evol. 2025 Apr 1;42(4). doi: 10.1093/molbev/msaf071.
The bitter taste perception, crucial for avoiding harmful foods, is mediated by Tas2r taste receptors in vertebrates. Vultures are obligate scavengers of considerable conservation concern, consisting of Old World and New World vultures. While vultures primarily subsist on carrion, which contains various bitter secondary metabolites produced by microbes, their ability to sense bitterness remains unclear. In this work, we identified all Tas2r genes from the genomes of 6 vultures and 22 other Accipitriformes birds. Our analysis revealed that every species, except the osprey, possessed intact Tas2r1 and Tas2r2 genes. We observed the lack of genetic divergence in Tas2r1 among all species and relaxation of functional constraint in Tas2r2 in New World vultures. Molecular docking simulations revealed reduced binding affinity of Tas2r2 in New World vultures after testing 843 bitter compounds. Additionally, we conducted cell-based functional assays for Tas2r2 to assess its responsiveness to 24 natural bitter compounds with diverse chemical structures, and confirmed lower responsiveness in New World vultures compared to other birds. These findings suggest a functional decline of bitter taste perception in New World vultures, not observed in Old World vultures, aligning with functional relaxation and reduced binding affinity of Tas2r2 predicted in New World vultures. The functional decline of bitter taste may compromise their natural defense against synthetic bitter pesticides or veterinary drugs, highlighting the potential risks faced by New World vultures in contemporary environments.
苦味感知对于避免摄入有害食物至关重要，在脊椎动物中由Tas2r味觉受体介导。秃鹫是具有重要保护意义的专性食腐动物，包括旧大陆秃鹫和新大陆秃鹫。虽然秃鹫主要以腐肉为食，腐肉中含有微生物产生的各种苦味次生代谢产物，但它们感知苦味的能力仍不清楚。在这项研究中，我们从6种秃鹫和22种其他鹰形目鸟类的基因组中鉴定出了所有Tas2r基因。我们的分析表明，除了鹗之外，每个物种都拥有完整的Tas2r1和Tas2r2基因。我们观察到所有物种的Tas2r1基因缺乏遗传差异，而新大陆秃鹫的Tas2r2基因功能限制有所放松。分子对接模拟显示，在测试了843种苦味化合物后，新大陆秃鹫的Tas2r2结合亲和力降低。此外，我们对Tas2r2进行了基于细胞的功能测定，以评估其对24种具有不同化学结构的天然苦味化合物的反应性，并证实新大陆秃鹫与其他鸟类相比反应性较低。这些发现表明，新大陆秃鹫的苦味感知功能下降，而旧大陆秃鹫未观察到这种情况，这与新大陆秃鹫中预测的Tas2r2功能放松和结合亲和力降低一致。苦味感知功能的下降可能会损害它们对合成苦味农药或兽药的天然防御能力，凸显了新大陆秃鹫在当代环境中面临的潜在风险。
