Multiple cellular roles of Neurospora crassa plc-1, splA2, and cpe-1 in regulation of cytosolic free calcium, carotenoid accumulation, stress responses, and acquisition of thermotolerance

Phospholipase Cl (PLC1), secretory phospholipase A2 (sPLA2) and Ca2+/H+ exchanger proteins regulate calcium signaling and homeostasis in eukaryotes. In this study, we investigate functions for phospholipase Cl (plc-1), sPLA2 (splA2) and a Ca2+/H+ exchanger (cpe-1) in the filamentous fungus Neurospora crassa. The Delta plc-1, Delta splA2, and Delta cpe-1 mutants exhibited a growth defect on medium supplemented with the divalent ionophore A23187, suggesting that these genes might play a role in regulation of cytosolic free Ca2+ concentration ([Ca2+](c)) in N. crassa. The strains lacking plc-1, splA2, and cpe-1 possessed higher carotenoid content than wild type at 8 degrees C, 22 degrees C, and 30 degrees C, and showed increased ultraviolet (UV)-survival under conditions that induced carotenoid accumulation. Moreover, Delta plc-1, Delta splA2, and Delta cpe-1 mutants showed reduced survival rate under hydrogen peroxide-induced oxidative stress and induced thermotolerance after exposure to heat shock temperatures. Thus, this study revealed multiple cellular roles for plc-1, splA2, and cpe-1 genes in regulation of [Ca2+](c), carotenoid accumulation, survival under stress conditions, and acquisition of thermotolerance induced by heat shock.