The Hydra FGF family - dispersed across the genome and expressed locally.

Abstract

Although the nonbilaterian Hydra has a simple body architecture, its signaling systems are as complex as those of Bilateria. We here add data to the fibroblast growth factor signaling system which has previously been identified in Hydra as essential for bud detachment. The localized expression patterns of its, now fifteen, FGFs indicate additional, yet unidentified, functions in sometimes very small subsets of cells at the body termini and/or during budding or in testes. Presence of a typical signal sequence (prediction >93%) in only 30% of the Hydra FGFs suggests mechanisms of action (and/or secretion) other than the canonical ones. A knockdown approach using siRNA revealed a potential role for Hv-FGF-c in tentacle morphogenesis. Our results document a high complexity of FGF signaling sites in Hydra and open the field for a detailed analysis of their functions.