Wang Kai, Zhao Huabin
Department of Ecology, College of Life Sciences, Wuhan University, Wuhan, China.
Department of Ecology, College of Life Sciences, Wuhan University, Wuhan, China
Genome Biol Evol. 2015 Sep 4;7(9):2705-15. doi: 10.1093/gbe/evv180.
As they belong to the most species-rich class of tetrapod vertebrates, birds have long been believed to possess an inferior taste system. However, the bitter taste is fundamental in birds to recognize dietary toxins (which are typically bitter) in potential food sources. To characterize the evolution of avian bitter taste receptor genes (Tas2rs) and to test whether dietary toxins have shaped the repertoire size of avian Tas2rs, we examined 48 genomes representing all but 3 avian orders. The total number of Tas2r genes was found to range from 1 in the domestic pigeon to 12 in the bar-tailed trogon, with an average of 4, which suggested that a much smaller Tas2r gene repertoire exists in birds than in other vertebrates. Furthermore, we uncovered a positive correlation between the number of putatively functional Tas2rs and the abundance of potential toxins in avian diets. Because plant products contain more toxins than animal tissues and insects release poisonous defensive secretions, we hypothesized that herbivorous and insectivorous birds may demand more functional Tas2rs than carnivorous birds feeding on noninsect animals. Our analyses appear to support this hypothesis and highlight the critical role of taste perception in birds.
由于鸟类属于四足脊椎动物中物种最为丰富的类群，长期以来人们一直认为它们的味觉系统较差。然而，苦味对于鸟类识别潜在食物来源中的饮食毒素（通常是苦味的）至关重要。为了描述鸟类苦味受体基因（Tas2rs）的进化，并测试饮食毒素是否塑造了鸟类Tas2rs的基因库大小，我们检查了代表除3个鸟类目之外所有鸟类目的48个基因组。结果发现，Tas2r基因的总数在家鸽中为1个，在斑尾咬鹃中为12个，平均为4个，这表明鸟类的Tas2r基因库比其他脊椎动物小得多。此外，我们发现推定具有功能的Tas2rs数量与鸟类饮食中潜在毒素的丰度之间存在正相关。由于植物产品比动物组织含有更多毒素，并且昆虫会释放有毒的防御性分泌物，我们推测食草和食虫鸟类可能比以非昆虫动物为食的食肉鸟类需要更多具有功能的Tas2rs。我们的分析似乎支持这一假设，并突出了味觉感知在鸟类中的关键作用。
