Research On Regulation And Mechanism Of Cysteine Treatment On Senescence Of Postharvest Flammulina Veluminata

Flammulina velutipes have higher respiration and fresh fruiting body.Therefore,Flammulina velutipes are prone to deterioration and have a short shelf-life at ambient temperature in combination with losses of nutrition and quality.However,the quality control of postharvest Flammulina velutipes were mainly focused on the stipe,and there are few researches on cap.L-cysteine（Cys）has strong antioxidant activity and can effectively inhibit the browning of edible fungi.However,the regulation mechanism of exogenous Cys on the senescence process of edible fungi after harvest is not clear.Therefore,the effects of 20mmol·L^-1 Cys treatment on the quality,energy metabolism,cell wall metabolism and glutathione metabolism of postharvest Flammulina velutipes during low temperature storage were investigated in this paper.The main conclusions were as follows:（1）During the first 9 days of the storage period,Cys treatment significantly inhibited increase of the stipe elongation,cap opening and water content of fruiting body.So Cys treatment could effectively maintain good sensory quality of postharvest Flammulina velutipes.The energy level in the stipe was always higher than that in the cap during storage.Cys treatment delayed the decrease of ATP and ADP contents,promoted the activities of succinate dehydrogenase（SDH）,H⁺-ATPase and Ca²⁺-ATPase.And Cys treatment could effectively inhibit the increase of ascorbate peroxidase（CCO）activity in the early stage of storage.Therefore,20 mmol·L^-1 Cys treatment could delay the deterioration of Flammulina velutipes quality and maintain a higher energy level in tissues.（2）During storage,The activities of chitinase（CHT）,β-1,3-glucanase（GLU）and cellulose（Cx）in cap were higher than that in stipe.The activities of cinnamyl alcohol dehydrogenase（CAD）and peroxidase（POD）in the stipe were higher than that in the cap,which resulted in the difference in senescence degree of the cell wall between the stipe and cap.However,there was no significant correlation between phenylalanine ammonia-lyase（PAL）activity and lignin content（P>0.05）.During the whole storage period,Cys treatment significantly delayed the increase of chitin content and the activities of CHT and GLU.At the same time,Cys treatment also maintained higher cellulose content and lower cellulase activity.And the synthesis of lignin in mushroom was promoted by improving the activities of CAD and POD in Cys treatment.Therefore,20 mmol·L^-1 Cys treatment could delay the softening and extension of cell wall during senescence and maintain the hardness of mushroom body.（3）The levels of glutathione（GSH）and ascorbic acid（AsA）in stipe were higher than that in cap during the whole storage stage.Because Cys treatment could significantly increase activity of Glutathione reductase（GR）,the content of GSH,Oxidized glutathione（GSSG）,total GSH,AsA,Dehydroascorbic acid（DHA）and total AsA.Hence,Cys treatment could maintain the higher antioxidant level of Flammulina velutipes during storage,In the middle of storage,Cys treatment up regulated the gene expression of FvGPX1,FvGPX2,FvGST1,FvGST2,FvGST3 in GSH metabolic pathway and FvG6PDH,Fv6PGDH1,Fv6PGDH2 in PPP pathway.In the early stage of storage,Cys treatment up regulated FvGGT expression.These results indicated that these genes were more likely to be involved in the regulation of GSH metabolic pathway in Flammulina velutipes,and their response patterns to Cys treatment were different during storage.