ABSTRACT
Blade cells of the green macroalga Ulva mutabilis Føyn (Chlorophyta) excrete regulatory factors into their cell wall and growth medium to control the status of the cell. These unknown sporulation inhibitors: a glycoprotein (SI-1) and a small molecular weight compound (SI-2) located within the bilayer of Ulva, control the vegetative status of the cell. On removal of the sporulation inhibitors by mincing the mature thallus into small single-layered fragments and washing intensively, the gametogenesis of the thalli can be artificially initiated. Although this differentiation of a blade cell was investigated mainly for the gametogenesis, a similar regulation was also observed in sporogenesis, which results in the release of zooids. During the sporulation process, a further low-molecular weight compound, the swarming inhibitor (SWI), accumulates within the growth medium and controls the discharge of the germ cells on the third day on the induction of sporulation. Neither these inhibitors nor the signaling pathways inducing gametogenesis have been characterized so far. Therefore, it is tempting to assume that those inhibitors in hand allow us to manipulate the life cycle of land-based aquaculture by applying a nongenetic approach. A protocol is suggested for the direct application in bioassays and aquaculture practices, to try to isolate all the inhibitors with an all-in-one workflow.
