Early origin of the bilaterian developmental toolkit - PubMed (original) (raw)

Early origin of the bilaterian developmental toolkit

Douglas H Erwin. Philos Trans R Soc Lond B Biol Sci. 2009.

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).

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Figures

Figure 1.

Figure 1.

A phylogenetic tree for metazoans scaled against the molecular clock dates of Peterson et al. (2008). The ages of nodes are well calibrated by the molecular clock results of Peterson et al. and are shown as black boxes.

Figure 2.

Figure 2.

Ediacaran fossils mentioned in the text. (a) Fracofusus from Mistaken Point, Newfoundland, 14 cm. (b) Rangea from southern Namibia; 5 cm. (c) Kimberella from White Sea, Russia; anterior to right, with the anterior elongation, 9 cm. (d) Yorgia from the White Sea, Russia; anterior (?) up, about 18 cm. (e) Ernietta from southern Namibia, approximately 15 cm. (f) Dickinsonia from Ediacaran Hills, south Australia, 6 cm.

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References

    1. Adamska M., Degnan S. M., Green K. M., Adamski M., Craigie A., Larroux C., Degnan B. M.2007Wnt and TGF-beta expression in the sponge Amphimedon queenslandica and the origin of metazoan embryonic patterning. PLoS ONE 2, e1031 (doi:10.1371/journal.pone.0001031) - DOI - PMC - PubMed
    1. Arendt D., Nubler-Jung K.1994Inversion of dorso-ventral axis. Nature 371, 26 (doi:10.1038/371026a0) - DOI - PubMed
    1. Arendt D., Nubler-Jung K.1999Comparison of early nerve cord development in insects and vertebrates. Development 126, 2309–2325 - PubMed
    1. Arendt D., Technau U., Wittbrodt J.2001Evolution of the bilateria larval foregut. Nature 409, 81–85 (doi:10.1038/35051075) - DOI - PubMed
    1. Arendt D., Tessmar-Raible K., Snyman H., Dorresteijn A., Wittbrodt J.2004Ciliary photoreceptors with a vertebrate-type opsin in an invertebrate brain. Science 306, 869–871 (doi:10.1126/science.1099955) - DOI - PubMed

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