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

Members of the TGF‐β superfamily of signaling molecules are widespread in metazoans, but the evolutionary origin of particular subclasses of signaling mechanisms is poorly defined. The DPP/BMP class, for example, is implicated in dorsal‐ventral patterning, neural patterning, and limb development. Here we report the presence of several components of a DPP/BMP‐specific signal transduction cascade in a nonbilateral animal, the coral Acropora millepora. The discovery of these components, a putative type I receptor and two putative receptor‐activated Smads, suggests that DPP/BMP signaling predates both dorsal‐ventral pattern formation and limb development. We postulate that an ancestral role in neuroepithelial patterning may account for the high level of conservation between DPP/BMP signaling components found in this nonbilateral animal and the more complex triploblastic organisms of the arthropod and chordate phyla.