PAL-mediated phenylpropanoid metabolism contributes to storage stability of postharvest Pleurotus eryngii under hot air treatment

Hot air (HA) treatment improves the quality stability of P. eryngii during storage. HA treatment induces the activation of PAL to enhance phenylpropanoid metabolism. PePAL2 positively regulates the phenylpropanoid metabolism. Phenylpropanoid metabolism plays an essential role in storage stability of edible mushrooms. Phenylalanine ammonia-lyase (PAL) is the rate-limiting enzyme of this metabolic pathway. However, its special mechanisms in regulating postharvest quality of Pleurotus eryngii remain to be determined. This study aimed to investigate the roles of hot air (HA) and PAL inhibitor (AOPP) on the postharvest storage stability of P. eryngii to reveal the potential regulatory mechanism of PAL. Results showed that HA treatment inhibited the increase in water loss, browning, electrolyte leakage rate and malonaldehyde (MDA) content in P. eryngii . It also elevated the contents of phenylpropanoid metabolites and enhanced the activities and expression levels of the key enzymes in basic phenylpropanoid pathway. However, the activated phenylpropanoid metabolism induced by HA treatment was inhibited by AOPP treatment, leading to severe quality deterioration. To further analyze the role of PAL, the overexpression and silencing transformants of PePAL2 , one of the PAL homologous genes in P. eryngii , were constructed. The overexpression of PePAL2 up-regulated the expression of genes downstream of PAL and boosted the contents of secondary metabolites, whereas PePAL2 -silenced transformants showed the opposite effect, indicating that PePAL2 was crucial to the regulation of phenylpropanoid metabolism. Overall, the results suggested that HA treatment activated the phenylpropanoid metabolism through PePAL2 , thereby improving the storage stability of P. eryngii .