Pleurotus ostreatus (Jacq.) P. Kumm is the second most cultivated edible mushroom worldwide. Temperature is one of the main environmental factors affecting the growth and fructification of mushrooms. However, the effects of ambient temperature on the growth, development, and production of bag-cultured P. ostreatus are still unclear. In this study, eight ambient temperatures (15 °C, 18 °C, 20 °C, 22 °C, 25 °C, 28 °C, 30 °C, and 32 °C) were used to cultivate P. ostreatus mycelia with cottonseed hull as substrate. Then, the agronomic traits and the activities of substrate-degrading and antioxidant enzymes were determined. The mycelial growth and fructification of P. ostreatus differed significantly under different temperatures, and 22 °C was the optimum temperature for mycelial culture when we comprehensively analyzed all the agronomic traits. The mycelial growth rate and the biological efficiency under 22 °C were 0.56 cm/d and 99.53%, respectively. Furthermore, there were also significant differences in the activities of substrate-degrading enzymes and antioxidant enzymes under different ambient temperatures. The highest activities of lignocellulose-degrading enzymes (laccase, xylanase, and cellulase), amylase, and proteinase at the vegetative growth stage occurred at 15–22 °C, 20–22 °C, and 22–30 °C, respectively. The highest activities of superoxide dismutase, peroxidase, and catalase at the vegetative growth stage occurred at 28–30 °C. This study provides a reference temperature for bag-cultured P. ostreatus.

Pleurotus ostreatus (Jacq.) P. Kumm is cultivated worldwide, and its growth is seriously threatened by heat stress. Here, we performed a comprehensive analysis to investigate the influence of the phytohormone salicylic acid (SA) in P. ostreatus under HS. The results showed that the hyphal growth recovery rate and the antioxidant capacity of P. ostreatus increased with exogenous SA application (0.01 mmol/L and 0.05 mmol/L) after HS treatment. Metabolomic and transcriptomic analyses showed that SA application (0.05 mmol/L) weakened central carbon metabolism to allow cells to survive HS efficiently. In addition, SA shifted glycolysis to one-carbon metabolism to produce ROS scavengers (GSH and NADPH) and reduced ROS production by altering mitochondrial metabolism. SA also maintained nucleotide homeostasis, led to membrane lipid remodeling, activated the MAPK pathway, and promoted the synthesis of cell-wall components. This study provides a reference for further study of SA in microorganisms.

Pleurotus ostreatus (Jacq.) P. Kumm has high medicinal value, but few studies exist on regulating secondary metabolite biosynthesis. Environmental factors play a substantial role in the accumulation of microbial secondary metabolites. In this study, the effects of heat stress (24 h) and salicylic acid (0.05 mmol/L) treatment on the secondary metabolism of P. ostreatus were analyzed by metabolome, transcriptome, and gene differential expression analysis. Metabolome and transcriptome analyses showed that salicylic acid significantly increased the accumulation of antibiotics and polyketones, while heat stress increased the accumulation of flavonoids, polyketones, terpenoids, and polysaccharides. The content and the biosynthetic genes expression of heparin were markedly increased by heat stress, and the former was increased by 4565.54-fold. This study provides a reference for future studies on secondary metabolite accumulation in edible fungi.

Pleurotus ostreatus is one of the most cultivated edible fungi worldwide, but its lignocellulose utilization efficiency is relatively low (<50 %), which eventually affects the biological efficiency of P. ostreatus. Improving cellulase production and activity will contribute to enhancing the lignocellulose-degrading capacity of P. ostreatus. AMP-activated/Snf1 protein kinase plays important roles in regulating carbon and energy metabolism. The Snf1 homolog (PoSnf1) in P. ostreatus was obtained and analyzed using bioinformatics. The cellulose response of PoSnf1, the effect of the phosphorylation level of PoSnf1 on the expression of cellulose degradation-related genes, the putative proteins that interact with the phosphorylated PoSnf1 (P-PoSnf1), the cellobiose transport function of two sugar transporters (STP1 and STP2), and the interactions between PoSnf1 and STP1/STP2 were studied in this research. We found that cellulose treatment improved the phosphorylation level of PoSnf1, which further affected cellulase activity and the expression of most cellulose degradation-related genes. A total of 1, 024 proteins putatively interacting with P-PoSnf1 were identified, and they were enriched mainly in the substances transport and metabolism. Most of the putative cellulose degradation-related protein-coding genes could respond to cellulose. Among the P-PoSnf1-interacting proteins, the functions of two sugar transporters (STP1 and STP2) were further studied, and the results showed that both could transport cellobiose and were indirectly regulated by P-PoSnf1, and that STP2 could directly interact with PoSnf1. The results of this study indicated that PoSnf1 plays an important role in regulating the expression of cellulose degradation genes possibly by affecting cellobiose transport.