Induction of germination in Blastocladiella emersonii by cyclic AMP and inhibitors of cyclic AMP phosphodiesterase.

Since K+-induced germination of Blastocladiella emersonii is accompanied by a rapid decrease of a specific cyclic AMP phosphodiesterase (cAMP PDE) activity and a transient cyclic AMP accumulation, the effects of this compound as well as of some inhibitors of cAMP PDE on the induction of germination were tested. Adenine and caffeine, competitive inhibitors of zoospore cAMP PDE, were able to elicit germination in substitution for K+. Cyclic AMP is a poor inducer, but a synergistic effect was evident when non-effective concentrations of K+ and cyclic AMP were added together to the medium. At the same concentration, cyclic GMP had no effect as compared with cyclic AMP. Lanthanum, a specific antagonist of calcium in several biological systems, completely blocked the germination induced by potassium.