Contrasting mode of evolution at a coat color locus in wild and domestic pigs.
Contrasting mode of evolution at a coat color locus in wild and domestic pigs.
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DOI：
10.1371/journal.pgen.1000341
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发表时间：
2009-01
期刊：
影响因子：
4.5
通讯作者：
Andersson L
中科院分区：
文献类型：
--
作者：
Fang M;Larson G;Ribeiro HS;Li N;Andersson L
尽管驯化过程在10,000年前才开始，但它已经导致了个体物种内一定程度的表型变异，这通常与更深的进化时间尺度有关。虽然在家畜中发现的许多可变性状是相对较新的人类介导的选择的结果，但不确定性仍然存在于现代普遍存在的长期可变性状（如毛色）是否是选择或漂移的结果，以及潜在的等位基因是否存在于野生祖先中或在驯化开始后出现。在这里，通过对猪黑素皮质素受体1（MC 1 R）位点序列多样性的调查，我们提供的证据表明，来自中国和欧洲的野生猪和家猪（Sus scrofa）单倍型是截然不同的选择压力的结果，毛色变异是驯化出现后出现的等位基因的有意选择的结果。亚洲和欧洲野猪（进化上不同的亚种）不同，只有同义替换，表明伪装毛色保持纯化选择。然而，在家猪中，9个独特的突变中的每一个都改变了氨基酸序列，从而产生了毛色多样性。大多数国内MC 1 R等位基因与野生型的差异超过一个突变，这意味着对毛色变体的强阳性选择的长期历史，在此期间，人类有樱桃挑选的罕见突变，这些突变在野生环境中会很快被消除。这种模式表明，毛色表型是由直接的人类选择，而不是通过简单的放松自然选择压力。这项研究解释了为什么家养动物的毛色如此多变，而它们的野生祖先的毛色却如此统一。具体来说，我们问这是否是（i）宽松的纯化选择的结果，（ii）在强选择（例如行为）下，一些突变会影响毛色和另一个性状，或者（iii）直接人类选择改变毛色表型。我们调查了来自欧洲和亚洲的野生和家猪中黑皮质素受体1（MC 1 R）基因的遗传变异。虽然我们在野猪和家猪中发现了相似数量的突变，但突变的性质却截然不同。在野猪中发现的所有突变都是沉默的，即，他们没有改变蛋白质序列。这意味着在野外有强大的净化选择，以保持迷彩服的颜色。相比之下，在家猪中发现的十分之九的突变改变了蛋白质序列，从而大大改变了所产生的毛色。这些结果表明，早期农民有意选择具有新毛色的猪。他们的动机可能很简单，比如对外来物种的偏好，或者选择减少伪装，以促进畜牧业和/或使驯化的形式与野生祖先不同。
Despite having only begun ∼10,000 years ago, the process of domestication has resulted in a degree of phenotypic variation within individual species normally associated with much deeper evolutionary time scales. Though many variable traits found in domestic animals are the result of relatively recent human-mediated selection, uncertainty remains as to whether the modern ubiquity of long-standing variable traits such as coat color results from selection or drift, and whether the underlying alleles were present in the wild ancestor or appeared after domestication began. Here, through an investigation of sequence diversity at the porcine melanocortin receptor 1 (MC1R) locus, we provide evidence that wild and domestic pig (Sus scrofa) haplotypes from China and Europe are the result of strikingly different selection pressures, and that coat color variation is the result of intentional selection for alleles that appeared after the advent of domestication. Asian and European wild boar (evolutionarily distinct subspecies) differed only by synonymous substitutions, demonstrating that camouflage coat color is maintained by purifying selection. In domestic pigs, however, each of nine unique mutations altered the amino acid sequence thus generating coat color diversity. Most domestic MC1R alleles differed by more than one mutation from the wild-type, implying a long history of strong positive selection for coat color variants, during which time humans have cherry-picked rare mutations that would be quickly eliminated in wild contexts. This pattern demonstrates that coat color phenotypes result from direct human selection and not via a simple relaxation of natural selective pressures. This study addresses why coat colors of domestic animals are so variable, while those of their wild ancestors are so uniform. Specifically, we asked whether this was the result of (i) relaxed purifying selection, (ii) that some mutations affect both coat color and another trait under strong selection (for instance behavior), or (iii) direct human selection for altered coat color phenotypes. We investigated genetic variation in the melanocortin receptor 1 (MC1R) gene among wild and domestic pigs from both Europe and Asia. Though we found a similar number of mutations in wild and domestic pigs, the nature of the mutations was strikingly different. All mutations found among wild boars were silent, i.e., they did not change the protein sequence. This implies strong purifying selection in the wild that maintains camouflage coat color. In contrast, nine out of ten mutations found in domestic pigs altered the protein sequence, thereby drastically transforming the resulting coat color. These results demonstrate that early farmers intentionally selected pigs with novel coat coloring. Their motivations could have been as simple as a preference for the exotic or selection for reduced camouflage to facilitate animal husbandry and/or to make the domesticated forms distinct from their wild ancestor.
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影响因子：
7.2
作者：
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通讯作者：
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