The Cell Functions of Phospholipase C-1, Ca2+/H+ Exchanger-1, and Secretory Phospholipase A2 in Tolerance to Stress Conditions and Cellulose Degradation in Neurospora Crassa.

We investigated the cell functions of the Ca 2+ signaling genes phospholipase C-1 ( plc-1 ), Ca 2+ / H + exchanger ( cpe-1 ), and secretory phospholipase A 2 ( splA 2 ) for stress responses and cellulose utilization in Neurospora crassa . The Δ plc-1 , Δ cpe-1 , and Δ splA 2 mutants displayed increased sensitivity to the alkaline pH and reduced survival during induced thermotolerance. The Δ splA 2 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 Δ splA 2 mutant could not grow on microcrystalline cellulose during ER stress. Furthermore, plc-1 , cpe-1 , and splA 2 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 Δ plc-1 , Δ cpe-1 , and Δ splA 2 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 Δ splA 2 and Δ cpe-1 ; Δ splA 2 mutants were due to increased cbh-1 , cbh-2 , and endo-2 expression in N. crassa . Therefore, plc-1 , cpe-1 , and splA 2 are involved in stress responses and cellulose utilization in N. crassa .