Changes Of Energy And Phenolic Substance In Postharvest Peach Fruit Based On Proteomic And LC/MS Techniques

Peach(Prunus persica L.)is most popular fruit in China which is rich in nutrition and economic value.Due to its perishable value,peach fruit has limited shelf life after harvest.During the bad sales time,the water loss and mildew factors will cause great loss to farmers.Until now,the technique of prolonging fruit shelf life is limited,applications like NO and 1-MCP arouse considerable attentions and have been widely investigated due to their advantages of high efficiency at relatively low concentrations and short treatment periods.As a climatic fruit,peach will undergo series of changes in texture,color,taste and flavor after postharvest.Fruit respiration can provide necessary energy to normal metabolism,and polyphenolic compound will directly affect its color,flavor and taste.Therefore,the aim of these research is to investigate protein expression in postharvest peach,try to find critical proteins or enzymes which can affect energy and polyphenolic metabolism using proteomics technique.We also study the single phenolic compound and critical gene using qPCR and LC/MS.Furthermore,we investigate the influence the 1-MCP and NO treatment on energy and phenolic metabolism,and to provide a reference for the molecular mechanism of ripening and senescence of peach fruit.The main results are as follows:1.Peach fruit from different time points was explored the total expression using iTraq technique.We successfully identified 64 proteins with more than 1.5-fold(p≤0.01),including those associated with energy metabolism(17%),carbohydrate metabolism(9%),response to stress(14%),lipid metabolism(5%),nucleotide metabolism(3%),amino acid metabolism(14%),flavone,and flavonol biosynthesis(3%),others and unknown(35%).Majority of energy production and carbohydrate metabolism related proteins showed decreased tendency during storage.Some novel proteins like Transcription factor bHLH135,UDP-glycosyltransferase,Cysteine proteinase inhibitor 5,Serine carboxypeptidase showed great potential capacity in response to external stress.Proteins associated with flavonoid biosynthesis revealed critical roles in color change of peach in ripening stages.2.To better understand mitochondrial roles in maintaining and regulating metabolism in storage tissues,highly purified mitochondria were isolated from peach tissue stored at 4℃ and 25℃,respectively,and their proteome was conducted using the method of 2-DE and MALDI-TOF/TOF.Twenty-four(24)differentially expressed proteins(2-fold,p≤0.01)were identified out of more than 300 spots and were divided into six categories,including oxidative stress(34%),carbon metabolism(29%),respiratory chain(17%),amino acid metabolism and protein biosynthesis(8%),heat shock protein(4%),ion channels(4%).Proteins involved in antioxidative systems,gluconeogenesis,glycolysis,ethanol fermentation were changed significantly in response to high temperature.Storage at 4℃dramatically delayed ripening and senescence processes by postponing the climacteric peak,slowing down carbon metabolism and degradation of cell structure.Besides,low temperature induced the expression of formate dehydrogenase and alanine-glyoxylate aminotransferase 2 homolog 2.Proteins classified in respiratory chain,ion channels and NADP-dependent malic enzyme showed high coherence with climacteric respiratory burst,and the antioxidative enzymes showed relatively important symptoms on ROS scavenging through orderly expressions.3.Peach fruit treated with 1-MCP(10 uL L-1 12 h)or NO(10 uL L-1 3 h)was stored in 25℃ for 8 days.The phenolic composition and change trend were evaluated by qPCR and LC/MS.After LC/MS analysis,20 phenolic compounds were successfully identified including anthocyanins,flavanones,flavanols,flavones,flavonols,and phenolic acid.1-MCP application inhibited the ethylene and CO2 production and stimulated the total phenol and total flavonoid contents.The scavenging capacities of DPPH,HO·,and O2·-after 1-MCP treatment were enhanced.The trend of mitochondrial respiration enzyme activity coincides with respiration tendency.1-MCP treatment affected the tissue color change,stimulated gene expression of PpaPAL,PpaCHS,PpaF3H,and PpaUFGT,and promoted the biosynthesis of flavonoids and stability of anthocyanin.PpaDFR and PpaUFGT played crucial roles in rapid color change stages.Kaempferol and kaempferol 3-O-galactoside increased distinctively during storage time.4.Unlike 1-MCP treatment,application with NO didn’t show apparent effect on ethylene and CO2 production.The trend SDH enzyme activity coincide with respiration tendency.NO treatment remarkably activated antioxidant enzyme and enhanced total phenol and total flavonoid contents.The scavenging capacities of DPPH,HO·,and O2·-after NO treatment were enhanced.Anthocyanin synthesis closely related to the change of ethylene.NO treatment inhibited anthocyanin synthesis but situmulate dihydroquercetin and 3-caffeoylquinic acid accumulation.