The cell functions of phospholipase C-1, Ca/H exchanger-1, and secretory phospholipase A in tolerance to stress conditions and cellulose degradation in Neurospora crassa.

We investigated the cell functions of the Ca signaling genes phospholipase C-1 (plc-1), Ca/H exchanger (cpe-1), and secretory phospholipase A (splA) for stress responses and cellulose utilization in Neurospora crassa. The Δplc-1, Δcpe-1, and ΔsplA mutants displayed increased sensitivity to the alkaline pH and reduced survival during induced thermotolerance. The ΔsplA mutant also exhibited hypersensitivity to the DTT-induced endoplasmic reticulum (ER) stress, increased microcrystalline cellulose utilization, increased protein secretion, and glucose accumulation in the culture supernatants. Moreover, the ΔsplA mutant could not grow on microcrystalline cellulose during ER stress. Furthermore, plc-1, cpe-1, and splA synthetically regulate the acquisition of thermotolerance induced by heat shock, responses to alkaline pH and ER stress, and utilization of cellulose and other alternate carbon sources in N. crassa. In addition, expression of the alkaline pH regulator, pac-3, and heat shock proteins, hsp60, and hsp80 was reduced in the Δplc-1, Δcpe-1, and ΔsplA single and double mutants. The expression of the unfolded protein response (UPR) markers grp-78 and pdi-1 was also significantly reduced in the mutants showing growth defect during ER stress. The increased cellulolytic activities of the ΔsplA and Δcpe-1; ΔsplA mutants were due to increased cbh-1, cbh-2, and endo-2 expression in N. crassa. Therefore, plc-1, cpe-1, and splA are involved in stress responses and cellulose utilization in N. crassa.