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Philos Trans R Soc Lond B Biol Sci. 2009 Aug 12;364(1527):2253-61. doi: 10.1098/rstb.2009.0038.

Early origin of the bilaterian developmental toolkit.

Author information

1
Department of Paleobiology, MRC-121, National Museum of Natural History, Washington, DC 20013-7012, USA. erwind@si.edu

Abstract

Whole-genome sequences from the choanoflagellate Monosiga brevicollis, the placozoan Trichoplax adhaerens and the cnidarian Nematostella vectensis have confirmed results from comparative evolutionary developmental studies that much of the developmental toolkit once thought to be characteristic of bilaterians appeared much earlier in the evolution of animals. The diversity of transcription factors and signalling pathway genes in animals with a limited number of cell types and a restricted developmental repertoire is puzzling, particularly in light of claims that such highly conserved elements among bilaterians provide evidence of a morphologically complex protostome-deuterostome ancestor. Here, I explore the early origination of elements of what became the bilaterian toolkit, and suggest that placozoans and cnidarians represent a depauperate residue of a once more diverse assemblage of early animals, some of which may be represented in the Ediacaran fauna (c. 585-542 Myr ago).

PMID:
19571245
PMCID:
PMC2873006
DOI:
10.1098/rstb.2009.0038
[Indexed for MEDLINE]
Free PMC Article
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