Isolation of a putative peroxidase, a target for factors controlling foot-formation in the coelenterate hydra

In hydra, differentiated ectodermal cells of the foot region contain a peroxidase activity that can be used as a marker for foot-specific differentiation processes. Because the expression of the gene coding for the peroxidase must be tightly regulated during foot-specific differentiation, characterization of the protein and cloning of the corresponding gene should provide valuable tools for getting deeper insights into the regulation of foot-specific differentiation. In this paper we characterize the foot-specific peroxidase by biochemical, histochemical, and molecular biological methods. We show that it is localized in granules, and that it consists of a single component, the molecular mass of which is in the range of 43-45 kDa. Purification of the protein and subsequent cloning of its complementary DNA yielded two closely related clones, ppod1 and ppod2. Transcripts of ppod2 are abundant in the whole animal with the exception of the hypostome, the tentacles, and the foot; the expression of ppod1 matches exactly the localization of the foot-specific peroxidase.