Jiang Peihua, Josue-Almqvist Jesusa, Jin Xuelin, Li Xia, Brand Joseph G, Margolskee Robert F, Reed Danielle R, Beauchamp Gary K
Monell Chemical Senses Center, Philadelphia, Pennsylvania, United States of America.
Shaanxi Wild Animal Rescue and Research Center, Louguantai, China.
PLoS One. 2014 Mar 26;9(3):e93043. doi: 10.1371/journal.pone.0093043. eCollection 2014.
A growing body of behavioral and genetic information indicates that taste perception and food sources are highly coordinated across many animal species. For example, sweet taste perception is thought to serve to detect and motivate consumption of simple sugars in plants that provide calories. Supporting this is the observation that most plant-eating mammals examined exhibit functional sweet perception, whereas many obligate carnivores have independently lost function of their sweet taste receptors and exhibit no avidity for simple sugars that humans describe as tasting sweet. As part of a larger effort to compare taste structure/function among species, we examined both the behavioral and the molecular nature of sweet taste in a plant-eating animal that does not consume plants with abundant simple sugars, the giant panda (Ailuropoda melanoleuca). We evaluated two competing hypotheses: as plant-eating mammals, they should have a well-developed sweet taste system; however, as animals that do not normally consume plants with simple sugars, they may have lost sweet taste function, as has occurred in strict carnivores. In behavioral tests, giant pandas avidly consumed most natural sugars and some but not all artificial sweeteners. Cell-based assays revealed similar patterns of sweet receptor responses toward many of the sweeteners. Using mixed pairs of human and giant panda sweet taste receptor units (hT1R2+gpT1R3 and gpT1R2+hT1R3) we identified regions of the sweet receptor that may account for behavioral differences in giant pandas versus humans toward various sugars and artificial sweeteners. Thus, despite the fact that the giant panda's main food, bamboo, is very low in simple sugars, the species has a marked preference for several compounds that taste sweet to humans. We consider possible explanations for retained sweet perception in this species, including the potential extra-oral functions of sweet taste receptors that may be required for animals that consume plants.
越来越多的行为学和遗传学信息表明，在许多动物物种中，味觉感知和食物来源是高度协调的。例如，甜味感知被认为有助于检测并促使动物食用植物中提供热量的单糖。支持这一观点的是以下观察结果：大多数接受检查的食草哺乳动物都具有功能性甜味感知，而许多专性食肉动物则独立丧失了甜味受体的功能，对人类认为甜的单糖没有偏好。作为比较物种间味觉结构/功能的一项更大规模研究的一部分，我们研究了一种不以富含单糖的植物为食的食草动物——大熊猫（Ailuropoda melanoleuca）的甜味感知的行为和分子特性。我们评估了两种相互竞争的假设：作为食草哺乳动物，它们应该有一个发育良好的甜味系统；然而，作为通常不食用含单糖植物的动物，它们可能已经丧失了甜味功能，就像严格的食肉动物那样。在行为测试中，大熊猫热切地食用大多数天然糖以及部分但并非全部的人工甜味剂。基于细胞的检测揭示了甜味受体对许多甜味剂的类似反应模式。通过混合配对人类和大熊猫的甜味受体单元（hT1R2+gpT1R3和gpT1R2+hT1R3），我们确定了甜味受体中可能解释大熊猫与人类对各种糖类和人工甜味剂行为差异的区域。因此，尽管大熊猫的主要食物竹子的单糖含量非常低，但该物种对几种对人类来说有甜味的化合物有明显偏好。我们考虑了该物种保留甜味感知的可能解释，包括食用植物的动物可能需要的甜味受体的潜在口外功能。
