The delaying effect of a novel polyethylene nanopackaging on postharvest stipe elongation of Flammulina velutipes and its mechanism analysis

The stipe elongation is a typical characteristic of quality deterioration of postharvest Flammulina velutipes. We explored the delaying effect of a novel polyethylene nanopackaging (PENP) on stipe elongation in F. velutipes during storage and the underlying mechanism. The changes in quality, physical and chemical properties, and gene expression of F. velutipes in PENP during 18-day storage at low temperature were analyzed by morphological observation and physiological, biochemical, and transcriptomic methods. The results showed that PENP treatment could reduce the respiration of F. velutipes by maintaining higher CO2 and lower O2 content, decrease the stipe elongation rate and keep the postharvest storage quality of F. velutipes. PENP also inhibited the increase in chitin and & beta;-glucan content, the main components of the cell wall of F. velutipes, maintaining sufficient ATP content and energy charge (EC) values inside the stipe. Transcriptome analysis showed that PENP inhibited cell wall regeneration by down-regulating genes related to chitin degradation (Unigene0001917, Unigene0018811 and Unigene0007053) and & beta;-glucan degradation (Unigene0010562 and Unigene0010561), thus delaying stipe elongation. During the early stage of storage, PENP also inhibited energy metabolism by down-regulating succinate dehydrogenase (SDH), cytochrome c oxidase (CCO), and F1F0-ATPase-related genes involved in the oxidative phosphorylation pathway. In summary, PENP delayed postharvest stipe elongation of F. velutipes by inhibiting the synthesis of chitin and glucan in the cell wall and maintaining low energy metabolism in the stipe cells during early storage.