The induction of sporulation in the aquatic fungus Blastocladiella emersonii is dependent on extracellular calcium

Induction of sporulation in Blastocladiella emersonii is absolutely dependent on extracellular calcium. Vegetative cells grown in media with or without calcium do not sporulate in media devoid of calcium or in CaCl2 with EGTA. Calcium channel blockers, CoCl2 and nifedipine, and ionophore A23187 inhibited the induction of sporulation. The calmodulin antagonists trifluoperazine and chlorpromazine inhibited the sporulation when present in the cultures at least 60 min after induction. So, calcium that is accumulated during growth is not sufficient or is not mobilized to initiate sporulation, and a calcium influx is likely to occur by type II calcium channel functions, essential for the response to nutritional starvation. A calmodulin-like protein has been suggested to mediate calcium events in sporulation.