Coordinated regulation of enzymes and gene expression reveals thermotolerance mechanisms in Pleurotus giganteus

Thermotolerance is critical for the commercial cultivation of Pleurotus giganteus in tropical regions, especially under the impact of global climate change. This study investigated the thermotolerance mechanisms of two P. giganteus strains with contrasting heat responses: the heat-tolerant PG46 and heat-sensitive PG79. Phenotypic assessments, antioxidant and metabolic enzyme assays, and comparative transcriptome analyses were performed under heat stress at 40 °C. Both strains exhibited post-growth rings, reduced recovery, mycelial and membrane damage, which was more severe in PG79. Activities of antioxidant enzymes (superoxide dismutase, peroxidase, glutathione reductase, and catalase) and metabolic enzyme (laccase, cellulase, xylanase) initially increased and then declined, with PG46 consistently showing higher activity. Transcriptome analysis identified differentially expressed genes (DEGs) co-regulated in glycolysis, MAPK signaling, steroid biosynthesis, and protein processing pathways. In contrast, strain-specific expression patterns were observed in genes involved in ribonucleotide binding, zinc fingers, protein kinases, ubiquitination, cytochrome P450s, multicopper oxidases, MFS transporters, and 50S ribosome-binding GTPases, suggesting distinct molecular responses. Weighted Gene Co-expression Network Analysis (WGCNA) identified six gene modules associated with heat exposure duration and seven with thermotolerance. Key genes involved in signal transduction, protein processing, transferase activity, and macromolecule metabolism were identified. qRT-PCR validation of six selected genes confirmed RNA-seq reliability. These findings provided comprehensive insights into thermotolerance mechanisms in P. giganteus, offering specific gene targets and regulatory pathways for genetic improvement, precision breeding, and optimized cultivation strategies under heat stress conditions.