| Xiangshui pear,also known as Ruaner pear,belongs to the Pyrus ussuriensis Maxim system.Compared with other pears,Xiangshui pear is a cold-resistant,high-yield variety that grows in the dank mountainous areas with relatively high altitudes.Favored by consumers for its flavor and nutritional value,it is especially rich in ascorbic acid,phenols,dietary fiber,carotenoids and minerals.As the planting area and output increase year by year,its storage volume also shows an upward trend year by year.However,fruit farmers only rely on experience and lack scientific and standardized management,resulting in improper storage of Xiangshui pears,resulting in excessive accumulation of postharvest ethanol,odor generation,short storage period and high spoilage rate,which seriously affects the fruit flavor,quality,edible value and commercial value.In view of this situation,this study took the characteristic fruit of Haiyuan County,Ningxia,as the object,and carried out the study on the ethanol metabolism of postharvest Xiangshui pear in the process of storage at room temperature with different concentrations of 1-MCP.The combination of omics and metabolomics was used to explore the differences in genes and metabolites stored in Xiangshui pear fruit after treatment with 1-MCP at room temperature,and to determine the feasibility of the specific molecular mechanism of 1-MCP on the fresh-keeping ability of Xiangshui pears fruit.The study further analyzed the relationship between its physiological characteristics and biological information by comparing the ethanol metabolism rules,gene numbers and metabolites of Xiangshui pears fruits at different storage time points,and revealed the regulatory mechanism of 1-MCP on the fumigation of Xiangshui pears fruits.It has theoretical guiding significance for the effective storage and preservation measures of Xiangshui pears fruit.The main findings are as follows:1.Under normal temperature(20+1)℃ storage conditions,the fruit storage quality and ethanol metabolism of Xiangshui pears were studied by different concentrations of 1-MCP(0,0.5,1.0,1.5μL·L-1),1 The fruit quality of the-MCP treatment group was obviously better than that of the fruit without the 1-MCP treatment group.Mainly in:effectively delaying the decline of fruit firmness during storage;significantly inhibiting soluble solids(SSC),color difference L*value,a*value and b*rising rate and titratable acid(TA),ascorbic acid(VC)The rate of decline;the rate of fruit decay and the rate of increase of pyruvate content during storage were reduced;the accumulation of acetaldehyde and ethanol was inhibited;the activities of key enzymes pyruvate decarboxylase(PDC)and alcohol dehydrogenase(ADH)were reduced.The effect of 1.0 μL·L-1 1-MCP treatment was significantly higher than that of other treatment groups,inhibiting ethanol accumulation and delaying fruit ripening,maintaining fruit quality.It indicated that the appropriate concentration of 1-MCP treatment could maintain the fruit quality,good appearance and normal taste and flavor,and effectively alleviate and control the occurrence of "alcohol odor" during the storage process after harvesting.2.On the 0th,16th and 20th days of the storage period at room temperature(20+1)℃,the differentially expressed genes of the 1.0 μL·L-1 1-MCP treatment group and the CK group were compared.The results showed that:(1)Number of differentially expressed genes:A total of 21,898 genes were identified between the control group and the 1-MCP treatment group at 0 d,16 d and 20 d of storage,including 7,379 up-regulated genes and 14,519 down-regulated genes.Compared with the storage period,11491 genes were identified in the control group,of which 3497 genes were up-regulated and 7994 genes were down-regulated;compared with the 0 d of storage period,a total of 9,066 genes were identified on the 16th day,of which 3,387 genes were up-regulated and 5,679 were down-regulated.On the 20th day,a total of 11504 genes were identified,of which 3645 genes were up-regulated and 7859 genes were down-regulated.(2)Enrichment analysis of differentially expressed genes:Differentially expressed genes were classified into 20 biological processes,13 cellular components and 9 molecular functions.In biological processes,it is mainly involved in ethanol synthesis,other metabolic processes;in cellular components,it is mainly involved in mitochondrial membrane membrane,cell composition,cell structure,complexes and other GO items;in molecular functions,it is mainly involved in transport activities,transferase activities,transfer GO entries such as aldehyde group or ketone group,catalytic activity,etc.The enrichment rate of differential genes in secondary metabolite biosynthesis,metabolic pathways,steroid biosynthesis,plant hormone signal transduction,etc.is relatively high,and pyruvate decarboxylase(PDC)was found in the biosynthesis of secondary metabolites through localization annotation.Both PDC1 and PDC4 are enriched,and during fruit storage,PDC catalyzes pyruvate to produce acetaldehyde,and acetaldehyde is catalyzed by ADH to produce ethanol,thus achieving an impact on the fruit quality of Xiangshui pears;the metabolic pathway is found through KEGG positioning annotation to find the metabolism.Among the pathways,alcohol dehydrogenase and PDC were highly enriched;therefore,the interaction of various metabolic pathways in Xiangshui pears after harvesting jointly regulated fruit quality changes.(3)Changes in genes related to ethanol metabolism:The reaction process of ethanol metabolism is that pyruvate as a substrate is catalyzed by pyruvate decarboxylase(PDC)to generate acetaldehyde,which is catalyzed by alcohol dehydrogenase(ADH)produce ethanol.The up-regulated and down-regulated genes in the pyruvate metabolism pathway of Xiangshui pears fruit were more obvious during storage.The up-regulated genes of pyruvate kinase and aldehyde dehydrogenase indicated that they could promote the production of acetaldehyde and ethanol;the down-regulated genes of acid enolpyruvate carboxyl ylase,phosphoenolpyruvate carboxykinase(ATP),pyruvate kinase,lactylglutathione lyase,D-lactate dehydratase/protein deglycase,malate dehydrogenase(decarboxylation),apple Acid dehydrogenase(oxaloacetate-decarboxylation)(NADP+),malate dehydrogenase,acyl phosphatase,it is speculated that the main reason for the down-regulated gene formation is related to the decrease of pyruvate content in the fruit of Xiangshui pears in the later stage.3.On the 0 d,16 d and 20 d of the storage period at room temperature(20+1)℃,the differential metabolites and differential genes of the 1.0μL·L-1 1-MCP treatment group and the control group were compared,and the results showed that:(1)Differential metabolites:A total of 792 differential metabolites were identified in the positive ion analysis of Xiangshui pear fruit during storage.Compared with the control group,the treatment group had 603 up-regulated metabolites and 189 down-regulated metabolites;negative ion analysis had a total of 541 metabolites Differential metabolites,365 up-regulated metabolites and 177 down-regulated metabolites after 1-MCP treatment;including 50 carboxylic acids and their derivatives,24 organic oxides,20 benzene and substituted derivatives,17 flavonoids,12 glycerophospholipids,10 fatty acyl groups,6 steroids and steroid derivatives,7 purine nucleosides,6 pyridines and their derivatives,5 propanol lipids,4 phenols,3 kinds of indoles and derivatives,3 kinds of steroids and steroid derivatives,37 kinds(sugar alcohols,lignin lactones,keto acids and derivatives,etc.)and other substances;(2)Differential metabolites:significantly enriched in triterpenoids and tetracycline synthesis,the main enriched metabolic pathways are glucose metabolism,galactose metabolism,unsaturated fatty acid biosynthesis,starch and sucrose metabolism,fatty acid biosynthesis,leucine and isoleucine biosynthesis,ascorbic acid and uronic acid metabolism,while ether lipid metabolism only participates in a small number of metabolites.(3)Association analysis of ethanol metabolism,differential genes and differential metabolites:Through the joint pathway analysis of ethanol metabolism,differential genes and differential metabolites,the pathway of pyruvate metabolism to ethanol showed a strong correlation. |
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