The calmodulin pathway and evolution of elongated beak morphology in Darwin's finches
The calmodulin pathway and evolution of elongated beak morphology in Darwin's finches
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DOI：
10.1038/nature04843
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发表时间：
2006-08-03
期刊：
影响因子：
64.8
通讯作者：
Tabin, Clifford J.
中科院分区：
文献类型：
--
作者：
Abzhanov, Arhat;Kuo, Winston P.;Tabin, Clifford J.
自然选择下的适应性辐射的一个经典教科书例子是达尔文雀（燕雀科，雀形目）的14个密切相关物种的进化，其主要多样性在于它们喙的大小和形状（1-6）。因此，地雀有深而宽的喙，仙人掌雀有长而尖的喙（深度低，宽度窄），而莺雀有细长而尖的喙，反映了它们各自饮食的差异（6）。先前的研究表明，即使喙的三个主要尺寸（深度，宽度和长度）中的任何一个微小差异都会对鸟类的整体健康产生重大影响（3-7）。最近，我们使用了一种候选基因的方法来解释参与达尔文雀喙形态发生的一种途径（8）。然而，这种类型的分析仅限于已知与颅面和/或骨骼发育相关的分子。在这里，我们使用较少的限制，互补的DNA微阵列分析的成绩单中表达的喙原基找到以前未知的基因和途径，其表达与特定的喙形态。我们发现，钙调素（CaM），参与介导的Ca 2+信号的分子，表达在更高的水平在长而尖的喙的仙人掌雀比更强大的喙类型的其他物种。我们用原位杂交验证了这一观察结果。当这种钙调蛋白依赖途径的上调是人工复制在小鸡额鼻突出，它会导致上喙的伸长，重演的仙人掌雀的喙形态。我们的研究结果表明，钙调蛋白依赖性途径的局部上调可能是达尔文的雀类进化的一个组成部分，具有细长的喙形态，并提供了一个机制解释喙进化的独立性沿着不同的轴。更一般地说，我们的研究结果牵连钙调素依赖性途径在颅面骨骼结构的发育调节。
A classic textbook example of adaptive radiation under natural selection is the evolution of 14 closely related species of Darwin's finches (Fringillidae, Passeriformes), whose primary diversity lies in the size and shape of their beaks(1-6). Thus, ground finches have deep and wide beaks, cactus finches have long and pointed beaks ( low depth and narrower width), and warbler finches have slender and pointed beaks, reflecting differences in their respective diets(6). Previous work has shown that even small differences in any of the three major dimensions ( depth, width and length) of the beak have major consequences for the overall fitness of the birds(3-7). Recently we used a candidate gene approach to explain one pathway involved in Darwin's finch beak morphogenesis(8). However, this type of analysis is limited to molecules with a known association with craniofacial and/or skeletogenic development. Here we use a less constrained, complementary DNA microarray analysis of the transcripts expressed in the beak primordia to find previously unknown genes and pathways whose expression correlates with specific beak morphologies. We show that calmodulin (CaM), a molecule involved in mediating Ca2+ signalling, is expressed at higher levels in the long and pointed beaks of cactus finches than in more robust beak types of other species. We validated this observation with in situ hybridizations. When this upregulation of the CaM-dependent pathway is artificially replicated in the chick frontonasal prominence, it causes an elongation of the upper beak, recapitulating the beak morphology of the cactus finches. Our results indicate that local upregulation of the CaM-dependent pathway is likely to have been a component of the evolution of Darwin's finch species with elongated beak morphology and provide a mechanistic explanation for the independence of beak evolution along different axes. More generally, our results implicate the CaM-dependent pathway in the developmental regulation of craniofacial skeletal structures.