|Beschreibung:||Developmental gradients play a central role in axial patterning in the diploblastic Hydra. As part of the effort towards elucidating the molecular basis of these gradients as well as investigating the evolution of the mechanisms underlying axial patterning in metazoan animals, genes encoding signaling peptides are under investigation. I report the isolation and characterization of HyBMP5-8b, a BMP5-8 orthologue, from Hydra, a member of the diploblastic Cnidaria. Processes governing axial patterning are continuously active in adult Hydra. Expression patterns in normal animals and during bud formation were examined. These patterns, coupled with changes in patterns of expression in manipulated tissues during head regeneration, foot regeneration as well as under conditions that alter the positional value gradient indicate that the gene is active in three different processes. The gene plays a role in tentacle formation, in patterning the lower end of the body axis, and in early stages of head and foot organizer formation.