A Cell Wall-Associated Extracellular Catalase, Po CAT2, Confers Thermotolerance in Pleurotus ostreatus

Abstract Heat stress induces excessive extracellular H2O2 accumulation, compromising redox homeostasis and mushroom productivity. However, the role of extracellular catalases (CATs) in basidiomycetes remains poorly understood. Here, we identified PoCAT2, a cell wall-associated extracellular catalase in the basidiomycete Pleurotus ostreatus, whose secretion may involve a vesicle-mediated unconventional protein secretion pathway. Heat stress and exogenous H2O2 induced PoCAT2 expression and wall-associated catalase activity. Unlike intracellular PoCAT1, PoCAT2 overexpression increased catalase activity in both intracellular and cell wall compartments, enhancing in situ H2O2 scavenging and promoting mycelial growth under both optimal and elevated temperatures. Moreover, PoCAT2 overexpression accelerated fruiting and increased mushroom yield. These findings establish PoCAT2 as an extracellular antioxidant component that contributes to thermotolerance and fruiting performance in P. ostreatus, providing a potential strategy for improving thermotolerance in cultivated mushrooms.