| Zizania latifolia,belongs to Oryzae,is appreciated for its white color,tender texture,attractive aroma.It is an important vegetable with high nutritional and economical value and also used to prevent and treat metabolic disease.It is mainly harvested in the high temperature season from May to October,and its fresh-keeping period is shortened at normal temperature due to biotic and abiotic stress,and could be stored only for 2-3 days.In this study,transcriptomics and metabolomics techniques were used to study the effects of 1-MCP treatment on the expression of genes and metabolites in Z.latifolia during storage at normal temperature（25℃）.Combined with the analysis of physiological and biochemical indexes and ultrastructural observation,the molecular mechanism of 1-MCP regulating the postharvest senescence of Z.latifolia was explored,so as to provide theoretical basis for the mining of genes related to postharvest senescence and the breeding of anti-aging varieties.On these bases,the main results of our study are as follows:1.The result pointed out that a postharvest application of 1-MCP maintained the good visual appearance of fresh Z.latifolia,inhibited browning,weight loss and mildew at the bottom of Z.latifolia,and there is no significant change on L,a*,b*and△E during the whole storage period.In addition,1-MCP treatment inhibited the respiratory intensity of Z.latifolia during the first three days of storage,but it was significantly higher than that of the control on the sixth day of storage.Compared with the control,1-MCP treatment maintained relatively high SOD,CAT,APX activities and low PAL,POD,PLD,lipase and LOX activities,delayed the decline of ASA content,reduced the accumulation of O2-,H2O2 and MDA,and ultimately maintained the integrity of cell structure and delayed the senescence of Z.latifolia.In addition,Positive effects of 1-MCP on maintaining the cell structure integrity were observed in this investigation throughout the storage period at 25°C.2.Transcriptome analysis was used to analyze the gene expression changes of Z.latifolia treated with 1-MCP during storage at normal temperature.The results showed that there were5757 differentially expressed transcripts in the control group after 6 days of storage,including2595 up-regulated and 3162 down regulated differentially expressed transcripts;1-MCP treatment significantly increased the number of differentially expressed transcripts,the total number of differentially expressed transcripts was 6239,among which 2705 were up-regulated and 3534 down regulated.Molecular function analysis of Gene Ontology（GO）showed that these differential transcripts were mainly involved in antioxidant,binding,catalysis,electron transport,enzyme regulation,metal chaperone,molecular transport,nucleic acid transcription,nutrient accumulation,receptor,structural molecule,translation and transport activity.Furthermore,KEGG pathway analysis showed that signal transduction,translation,folding sorting and degradation,replication and repair,cell growth and death,transport and catabolism,carbohydrate metabolism,energy metabolism,amino acid metabolism and lipid metabolism were significantly enriched in Z.latifolia 6 days after storage.Moreover,pentose and glucuronic acid conversion,ascorbic acid and aldolic acid metabolism,photosynthesis,phosphoinositol metabolism,terpenoid biosynthesis,actin cytoskeleton and phenylpropane biosynthesis,plant hormone signal transduction,phenylpropane biosynthesis,diterpene biosynthesis,photosynthetic antenna protein and fatty acid prolongation were also significantly enriched.These results indicate that the senescence of Z.latifolia is related to many processes,such as material metabolism,active oxygen metabolism,signal transduction,cell growth and death.3.Metabolomic was used to analyze the changes of metabolites of Z.latifolia treated with1-MCP during storage at normal temperature.The results showed that:compared with CK0,460,493,472 and 529 metabolites were respectively identified in CK3,CK6,1-MCP3 and 1-MCP6,which were divided into 11 superclasses.KEGG pathway analysis also pointed out that these metabolites were involved in linoleic acid metabolism,amino acid biosynthesis,α-linolenic acid metabolism,alanine,aspartic acid and glutamate metabolism,amino acid t RNA biosynthesis,ABC transport,cyano-amino acid metabolism,carbon metabolism,arachidonic acid metabolism and phenylalanine,tyrosine and tryptophan biosynthesis.1-MCP treatment promoted significant enrichment of phenylalanine-tyrosine-tryptophan biosynthesis,tyrosine metabolism,oxidative phosphorylation,glycerolipid metabolism,nicotinic acid and nicotinamide metabolic pathway during normal temperature storage.4.Data integration obtained via correlation analysis highlighted a number of pathways and correlations between metabolites and transcripts involved in senescence as well as the regulatory processes.The results indicated that 1-MCP treatment significantly inhibited the up-regulated expression of plant hormone signal transduction pathway related genes such as NPR1,phosphotransfer protein gene and jasmonic acid content while promoted the up regulation of jasmonic acid amino acid synthase and BRI1 kinase inhibitor genes.In addition,1-MCP treatment significantly changed the expression pattern of genes related to MAPK signaling pathway,promoted the up regulation of serine/threonine phosphatase 2A gene,and delayed the down-regulation of phosphatidylethanolamine content.In addition,c AMP,involved in several intracellular signal cascades and able to stimulate the protein kinase A pathway of mitochondrial protein phosphorylation was up regulated under 1-MCP treatment.At the same time,1-MCP treatment also significantly promoted the down-regulation of phospholipase D gene and up-regulation of glutathione reductase gene,which was consistent with the decrease of oxidized glutathione content.These results suggest that 1-MCP treatment may delay the postharvest senescence of Z.latifolia by regulating the senescence related signal transduction pathways（such as MAPK,c AMP and jasmonic acid）,oxidative phosphorylation,reactive oxygen species metabolism,cell growth and death.These related pathways provide important molecular targets for the regulation of postharvest senescence of Z.latifolia. |
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