Gene expression divergence recapitulates the developmental hourglass model

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Item Type:	Article
Title:	Gene expression divergence recapitulates the developmental hourglass model
Creators Name:	Kalinka, A.T., Varga, K.M., Gerrard, D.T., Preibisch, S., Corcoran, D.L., Jarrells, J., Ohler, U., Bergman, C.M. and Tomancak, P.
Abstract:	The observation that animal morphology tends to be conserved during the embryonic phylotypic period (a period of maximal similarity between the species within each animal phylum) led to the proposition that embryogenesis diverges more extensively early and late than in the middle, known as the hourglass model. This pattern of conservation is thought to reflect a major constraint on the evolution of animal body plans. Despite a wealth of morphological data confirming that there is often remarkable divergence in the early and late embryos of species from the same phylum, it is not yet known to what extent gene expression evolution, which has a central role in the elaboration of different animal forms, underpins the morphological hourglass pattern. Here we address this question using species-specific microarrays designed from six sequenced Drosophila species separated by up to 40 million years. We quantify divergence at different times during embryogenesis, and show that expression is maximally conserved during the arthropod phylotypic period. By fitting different evolutionary models to each gene, we show that at each time point more than 80% of genes fit best to models incorporating stabilizing selection, and that for genes whose evolutionarily optimal expression level is the same across all species, selective constraint is maximized during the phylotypic period. The genes that conform most to the hourglass pattern are involved in key developmental processes. These results indicate that natural selection acts to conserve patterns of gene expression during mid-embryogenesis, and provide a genome-wide insight into the molecular basis of the hourglass pattern of developmental evolution.
Keywords:	Conserved Sequence, Biological Models, Developmental Gene Expression Regulation, Drosophila Proteins, Genetic Selection, Insect Genes, Insect Genome, Molecular Evolution, Oligonucleotide Array Sequence Analysis, Phylogeny, Species Specificity, Time Factors, Animals, Drosophila
Source:	Nature
ISSN:	0028-0836
Publisher:	Nature Publishing Group
Volume:	468
Number:	7325
Page Range:	811-814
Date:	9 December 2010
Official Publication:	https://doi.org/10.1038/nature09634
PubMed:	View item in PubMed

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