Conservation of a DPP/BMP signaling pathway in the nonbilateral cnidarian Acropora millepora

Members of the TGF-beta superfamily of signaling molecules are widespread i n metazoans, but the evolutionary origin of particular subclasses of signal ing mechanisms is poorly defined. The DPP/BMP class, for example, is implic ated in dorsal-ventral patterning, neural patterning, and limb development. Here we report the presence of several components of a DPP/BMP-specific si gnal transduction cascade in a nonbilateral animal, the coral Acropora mill epora. The discovery of these components, a putative type I receptor and tw o putative receptor-activated Smads, suggests that DPP/BMP signaling predat es both dorsal-ventral pattern formation and limb development. We postulate that an ancestral role in neuroepithelial patterning may account for the h igh level of conservation between DPP/BMP signaling components found in thi s nonbilateral animal and the more complex triploblastic organisms of the a rthropod and chordate phyla.