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

TitleTwo developmental modules establish 3D beak-shape variation in Darwin's finches.
Publication TypeJournal Article
Year of Publication2011
AuthorsMallarino, R, Grant, PR, B Grant, R, Herrel, A, Kuo, WP, Abzhanov, A
JournalProc Natl Acad Sci U S A
Date Published2011 Mar 08
KeywordsAnimals, Beak, beta Catenin, Biological Evolution, DNA, Complementary, Finches, Humans, Intercellular Signaling Peptides and Proteins, Oligonucleotide Array Sequence Analysis, Receptors, Transforming Growth Factor beta, Species Specificity

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.

Alternate JournalProc. Natl. Acad. Sci. U.S.A.
PubMed ID21368127
PubMed Central IDPMC3053969