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Two developmental modules establish 3D beak-shape variation in Darwin's finches

Author(s): Mallarino, Ricardo; Grant, Peter R.; Grant, B. Rosemary; Herrel, Anthony; Kuo, Winston P.; et al

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Abstract: Bird beaks display tremendous variation in shape and size, which is closely associated with the exploitation of multiple ecological niches and likely played a key role in the diversification of thousands of avian species. Previous studies have demonstrated some of the molecular mechanisms that regulate morphogenesis of the prenasal cartilage, which forms the initial beak skeleton. However, much of the beak diversity in birds depends on variation in the premaxillary bone. It forms later in development and becomes the most prominent functional and structural component of the adult upper beak/jaw, yet its regulation is unknown. Here, we studied a group of Darwin’s finch species with different beak shapes. We found that TGFβIIr, β-catenin, and Dickkopf-3, the top candidate genes from a cDNA microarray screen, are differentially expressed in the developing premaxillary bone of embryos of species with different beak shapes. Furthermore, our functional experiments demonstrate that these molecules form a regulatory network governing the morphology of the premaxillary bone, which differs from the network controlling the prenasal cartilage, but has the same species-specific domains of expression. These results offer potential mechanisms that may explain how the tightly coupled depth and width dimensions can evolve independently. The two-module program of development involving independent regulating molecules offers unique insights into how different developmental pathways may be modified and combined to induce multidimensional shifts in beak morphology. Similar modularity in development may characterize complex traits in other organisms to a greater extent than is currently appreciated.
Publication Date: 8-Mar-2011
Electronic Publication Date: 22-Feb-2011
Citation: Mallarino, R., Grant, P.R., Grant, B.R., Herrel, A., Kuo, W.P., Abzhanov, A. (2011). Two developmental modules establish 3D beak-shape variation in Darwin's finches. Proceedings of the National Academy of Sciences, 108 (10), 4057 - 4062. doi:10.1073/pnas.1011480108
DOI: doi:10.1073/pnas.1011480108
ISSN: 0027-8424
EISSN: 1091-6490
Pages: 4057 - 4062
Type of Material: Journal Article
Journal/Proceeding Title: Proceedings of the National Academy of Sciences
Version: Final published version. Article is made available in OAR by the publisher's permission or policy.

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