Localized expression of a dpp / BMP2 / 4 ortholog in a coral embryo

Abstract

As the closest outgroup to the Bilateria, the Phylum Cnidaria is likely to be critical to understanding the origins and evolution of body axes. Proteins of the decapentaplegic (DPP)͞bone morphogenetic protein (BMP) 2͞4 subfamily are central to the specification of the dorsoventral (D͞V) axis in bilateral animals, albeit with an axis inversion between arthropods and chordates. We show that a dpp͞BMP2͞4 ortholog (bmp2͞4-Am) is present in the reef-building scleractinian coral, Acropora millepora (Class Anthozoa) and that it is capable of causing phenotypic effects in Drosophila that mimic those of the endogenous dpp gene. We also show that, during coral embryonic development, bmp2͞4-Am expression is localized in an ectodermal region adjacent to the blastopore. Thus, a representative of the DPP͞BMP2͞4 subfamily of ligands was present in the common ancestor of diploblastic and triploblastic animals where it was probably expressed in a localized fashion during development. A localized source of DPP͞BMP2͞4 may have already been used in axis formation in this ancestor, or it may have provided a means by which an axis could evolve in triploblastic animals.

A simple visual system without neurons in jellyfish larvae

“…Scyphozoan larvae (Aurelia aurita and Cyanea capillata) also lack a gastric cavity (Widersten 1968). Interestingly, in the swimming Acropora planula, the oral opening is posteriorly compared with the direction of movement (Hayward et al 2002). The anterior-posterior polarity of a planula is defined not only by the direction of swimming, but also by the expression pattern of transcription factors and the formation of nerve cells (Grö ger & Schmid 2001).…”

“…Cnidarian larvae are of the planula type. The early development has been described morphologically and molecularly in great detail (Okada 1927;Hayward et al 2001Hayward et al , 2002. After fertilization of the egg and several cell divisions, a flattened blastula is formed, resembling a shallow bowl.…”

Finding partners: How BMPs select their targets

“…1). Ligands and downstream components of the signaling cascade have been found both in Cnidaria (metazoans that include Hydra, the anemone Nematostella, jellyfish, and corals), and also in the sponges, the most ancient metazoan clade (Suga et al, 1999;Hayward et al, 2002;Finnerty et al, 2004;Reinhardt et al, 2004;Rentzsch et al, 2006Rentzsch et al, , 2007Reber-Mü ller et al, 2006;Nichols et al, 2006;Adamska et al, 2007;Zoccola et al, 2009). Thus far, no TGF␤ superfamily signaling components have been reported in taxa "basal to" the sponges, including the single-celled choanoflagellates, fungi, or protozoa (Nichols et al, 2006;King et al, 2008).…”

Developmental gene expression provides clues to relationships between sponge and eumetazoan body plans

“…Analysis of the Wnt pathway components expression in the adult Pleurobrachia, demonstrating nested Wnt expression in the oral region, suggests that this feature might also be shared with ctenophores 25 . The second (dorsal-ventral) body axis in bilaterians is patterned by bone morphogenetic protein ligands of the Tgfb superfamily, which are also asymmetrically expressed along the directive axis of anthozoan cnidarians 26,27 .…”