Acetylation-modified phosphoglycerate dehydrogenase is associated with enhanced serine biosynthesis and one‑carbon metabolism, supporting heat resistance in Pleurotus ostreatus

Heat stress (HS) poses a significant threat to agricultural productivity. Pleurotus ostreatu, the second most cultivated edible fungus worldwide, is highly susceptible to HS, which disrupts cellular structures and metabolic homeostasis. Our previous studies revealed metabolic reprogramming under HS, particularly a strategic engagement of one‑carbon (1C) metabolism-a pathway whose functional significance in fungi remained unclear. Here, we investigate the mechanistic role of 1C metabolism in HS adaptation and its regulatory basis. Notably, HS did not alter the transcription of key 1C metabolic Enzymes but activated acetyltransferases, such as HAT, NAT1, NAT2, and NAT3. These Enzymes acetylated phosphoglycerate dehydrogenase (PHGDH) at lysine 394 (K394), which was associated with enhanced catalytic activity and increased serine biosynthesis. Elevated serine levels improved redox homeostasis by increasing GSH and NADPH levels and enhancing the activities of antioxidant Enzymes (SOD, CAT, and POD), thereby contributing to the mitigation of oxidative damage and thermotolerance. Previous study revealed that HS induced a reductive stress state, characterized by lactate accumulation and a decreased NAD+/NADH ratio. Within this metabolic context, HS-triggered acetylation at K394 may serve as a post-translational modification that is associated with activation of PHGDH, the gateway enzyme to serine and one‑carbon metabolism. This targeted activation may contribute to the production of Antioxidants (GSH and NADPH), potentially bolstering redox homeostasis and thermotolerance. These findings suggest a key mechanism by which PHGDH-mediated serine and one‑carbon metabolism may support redox balance and thermotolerance in P. ostreatus, offering a strategy for developing heat-resistant Fungal strains.