A MODEL FOR SIGNAL-TRANSDUCTION DURING GAMETE RELEASE IN THE FUCOID ALGA PELVETIA-COMPRESSA

Fucoid algae release gametes into-seawater following an inductive ligh t period (potentiation), and gamete expulsion from potentiated recepta cles of Pelvetia compressa began about 2 min after a light-to-dark tra nsition. Agitation of the medium reversed potentiation, with an expone ntial time course completed in about 3 h. Light regulated two signalin g pathways during potentiation and gamete expulsion: a photosynthetic pathway and a photosynthesis-independent pathway in which red light wa s active but blue light was not. Uptake of K+ appears to have an impor tant role in potentiation, because a 50% inhibition of potentiation oc curred in the presence of the tetraethylammonium ion, a K+-channel blo cker. A central role of anion channels in the maintenance of potentiat ion is suggested by the premature release of gametes in the light when receptacles were incubated with inhibitors of slow-type anion channel s. An inhibitor of tyrosine kinases, tyrphostin A63, also inhibited po tentiation. A model for gamete release from P. compressa is presented that proposes that illumination results in the accumulation of ions (e .g. K+) throughout the cells of the receptacle during potentiation, wh ich then move into the extracellular matrix during gamete expulsion to generate osmomechanical force, resulting in gamete release.