Transcriptomic analysis reveals the mechanism of ozone fumigation combined with polyethylene nanopackaging for delaying the browning and softening of mushrooms (Agaricus bisporus)

Browning and softening are typical characteristics of the postharvest quality degradation of button mushrooms. In this paper, comparative transcriptome analyses of mushroom samples during storage have been established based on sensory evaluations and physiological and biochemical indices analyses used to investigate the delaying effects of ozone fumigation combined with polyethylene nanopackaging (OCNP) on the browning and softening process, as well as their potential regulatory mechanisms. Our results indicated that the OCNP treatment reduced the respiratory rate of Agaricus bisporus, decreased the browning index and electrolyte leakage rate, and maintained the whiteness and firmness of postharvest mushrooms. In addition, OCNP inhibited the activities of browning-related enzymes (polyphenol oxidase and tyrosinase) and cell wall degrading enzymes (chitinase and β-1,3-glucanase) in the fruiting bodies, which delayed softening, while attenuating browning in A. bisporus. Transcriptomics analyses have revealed that OCNP inhibited the occurrence of browning by down-regulating genes involved in the antioxidant system (catalase and superoxide dismutase) as well as those related to browning enzymes (polyphenol oxidase and tyrosinase). Furthermore, OCNP also maintained the integrity of the cell walls by down-regulating genes associated with the degradation of cell wall components, such as chitin and β-1,3-glucan, thereby postponing softening. In summary, OCNP delayed the postharvest browning and softening of mushrooms by inhibiting the activity of browning-associated enzymes and mitigating the loss of cell wall components.