bZIP Transcription Factor Po bZIP8 Positively Mediates Heat Stress Tolerance and Negatively Regulates the Growth and Development of Pleurotus ostreatus

Pleurotus ostreatus is a globally cultivated edible and medicinal fungus, but its growth and yield are significantly affected by heat stress during cultivation. The basic leucine zipper (bZIP) transcription factors play a critical role in various biological processes, including development, growth, and abiotic stress responses. However, the role of the bZIP transcription factor in regulating the stress tolerance, growth and development of P. ostreatus remains poorly understood. In this study, PobZIP8 was cloned, revealing a 1632 bp open reading frame encoding 525 amino acids with a conserved bZIP domain. Subcellular localization confirmed PobZIP8 as a nuclear protein with transcriptional activation activity. We investigated the regulatory mechanisms of PobZIP8 in response to heat stress and the physiological characteristics and yield performance under different developmental stages. Overexpression of PobZIP8 enhanced mycelial tolerance to heat stress and improved recovery ability after stress. Physiological indicators showed that PobZIP8 can regulate antioxidant protective enzymes including peroxidase (POD) and superoxide dismutase (SOD) to eliminate excess reactive oxygen species, promote proline accumulation, and reduce the degree of membrane lipid peroxidation. However, PobZIP8 negatively regulated the growth and development of the fruiting body, delaying primordium and fruiting body formation and reducing fruiting body size and weight. Transcriptomic analysis exhibited that PobZIP8 regulated multiple metabolic and signalling pathways across different developmental stages, including ribosome biosynthesis, energy metabolism, antioxidant processes, and secondary metabolite synthesis. These findings suggest that PobZIP8 plays a dual role in balancing stress tolerance and growth, providing insights for improving both heat resistance and yield in P. ostreatus through genetic modification.