Iron Induces Proliferation and Morphogenesis in Primmorphs from the Marine Sponge Suberites domuncula

Dissociated cells from marine demosponges retain their proliferation capacity if they are allowed to form special aggregates, the primmorphs. On the basis of incorporation studies and septin gene expression, we show that Fe³⁺ ions are required for the proliferation of cells in primmorphs from Suberites domuncula. In parallel, Fe³⁺ induced the expression of ferritin and strongly stimulated the synthesis of spicules. This result is supported by the finding that the enzymatic activity of silicatein, converting organosilicon to silicic acid, depends on Fe³⁺. Moreover, the expression of a scavenger receptor molecule, possibly involved in the morphology of spicules, depends on the presence of Fe³⁺. We conclude that iron is an essential factor in proliferative and morphogenetic processes in primmorphs.