Analysis of Volatile Organic Compounds and Comparison of Heat Resistance Related Gene Expression in <i>Pleurotus ostreatus</i> Under Heat Stress

Heat stress induces oxidative stress in <i>Pleurotus ostreatus</i> (<i>P. ostreatus</i>), inhibiting the growth of both mycelium and fruiting bodies. While various studies have analyzed the physiological responses of <i>P. ostreatus</i> under heat stress conditions, comprehensive research comparing physiological responses in mycelium and fruiting bodies through metabolomic analysis of volatile organic compounds has not been conducted. In this study, we invested the levels of volatile organic compounds (VOCs), the activity of VOC synthesis-related enzymes, and the expression of heat resistance-related genes in mycelium and fruiting bodies exposed to heat stress. The total VOC levels measured in mycelium increased, whereas those in fruiting bodies decreased, indicating contrasting responses. In fruiting bodies, following heat stress, the synthesis of 1-Octen-3-ol was inhibited by glutathione peroxidase (GPx), and its conversion to 3-Octanone was accelerated by alcohol dehydrogenase (ADH), resulting in a significant decrease in 1-Octen-3-ol levels. In mycelium, both <i>GPx</i> gene expression levels and ADH activity remained unchanged under heat stress conditions, and 1-Octen-3-ol levels did not decrease. Comparison of heat resistance-related gene expression through quantitative PCR revealed that in mycelium, the expression of genes related to trehalose and heat shock proteins increased, while in fruiting bodies, the expression of genes related to antioxidant enzymes, including <i>GPx</i>, increased. In conclusion, we identified distinct heat resistance responses in mycelium and fruiting bodies, which had different effects on VOC synthesis, leading to contrasting changes.