DAVIDSON, B.J.*; MOODY, W.; SWALLA, B.: Metamorphic Competence in the Urochordates: Cloning of a Potential Competence Factor Involved in EGF Signaling

We are interested in elucidating the signals involved in coordinating urochordate post-larval development. Through suppressive PCR subtractions of staged Boltenia villosa larval and juvenile cDNAs, we have isolated transcripts differentially expressed during urochordate metamorphosis. A transcript homologous to the EGF signaling protein Cornichon was isolated in a subtraction focused on the acquisition of metamorphic competence. We have named this transcript Benjam (Boltenia EGF neighboring/juxtapositioning/activating? molecule). In situ hybridizations demonstrate that Benjam is differentially expressed in the anterior papillary region of competent Boltenia larvae. Research in the urochordate Herdmania curvata has demonstrated that the anterior papillary region secretes the EGF protein Hemps, which is both necessary and sufficient for the initiation of metamorphosis. Cornichon was first isolated in Drosophila where it has a role in regulating the EGF signaling involved in establishing the dorsal/ventral and anterior/posterior axis during oogenesis. Recent work in yeast has established a role for Cornichon in the directed secretion of targeted vesicles. Our hypothesis is that expression of Benjam acts to potentiate Hemps signaling thereby allowing Boltenia larvae to respond to metamorphic cues. Further research into this role for Benjam in urochordate metamorphic competence will provide insight into the function of Cornichon, which has a crucial but undefined role in EGF signaling. Additionally, a better understanding of urochordate metamorphosis will provide a foundation for exploring the evolution of metamorphosis within the chordates.