Transcriptome Sequencing And Ascorbic Acid Degradation Analysis Of'Hayward' Kiwifruit At The Mature Stage

Ascorbic acid(AsA)is the most important quality indicators for 'Hayward'kiwifruit but loss of AsA during the post-harvest storage leads to reduction of its nutrition.But its storage mechanism is rarely reported.In this research,high-throughput sequencing technique was used to study the transcriptions of three periods of post-harvest storage sampled from the first day(DAP1,Harvest day),the 15th day(DAP 15,Ethylene release peak)and the 24th day(DAP24,Ethylene is not released),respectively.Sequencing data of the three transcripts were analyzed.Sixteen genes were that selected to analyze the differential expression genes relating the AsA degradation pathway,including 10 ascorbic acid oxidase(AO)genes and 6 Laccase(Laccase)genes.Sixteen genes were analyzed by the molecular phylogenetic analysis which were further verified by real time quantitative PCR.Meanwhile,changes of AsA and the degradation of related enzymes were determined to reveal the AsA degradation in 'Hayward' during the storage,providing the theoretical basis for the study of kiwifruit storage and preservation technology.The results were as follows:1.Transcriptome Sequencing DataIn this reseach,mean of 4.43 Gb three transcripts data were obtained of,including 21,307 new transcripts with 19,392 coding transcript groups and 4512 new genes.Total of 7,090 differentially expressed genes were annotated into 114 KEGG biological pathways 2829,1728,336 and 5378,9668,4531 differential expression genes were up-regulated and down-regulated in DAP1 VS DAP15,DAP1 VS DAP24 and DAP15 VS DAP24.There were 9,6,6,7,8 up-regulated and 9,8,10,11,11 down-regulated differentially expressed genes in the signal transduction pathways of Abscisic acid,Cibberbllin,Cytokinine,Auxin and Ethylene,respectively.2.Analysis of Key Gene Expression of AsA Degradation PathwayIn the AsA degradation pathway,in the comparison of DAP 1 VS DAP 15,DAP1 VS DAP24 and DAP 15 VS DAP24,the genes that were up-regulated were 12,6,1 and the genes that were down-regulated were 8,13,8,respectively.It was found that the expression of the gene was down-regulated more than that of the gene was up-regulated with the prolongation of storage time.3.As A degradation Pathway Gene Expression by real time quantitative PCRIn this reseach,the relative expression of Laccase and AO gene was verified by real time quantitative PCR.The results showed that Achn059971 and Achn020161 were AO genes,which were the more higher in DAP15 and DAP24,15.49 and 22.36,13.18 and 19.13 respectively.Achn007661 andAchnl91341 were relatively expression higher in the Laccase gene,and the relative expression levels of DAP 15 and DAP24 were 12.23,30.25 and14.15,29.37,respectively.4.AsA degradation Key Enzymes AO and Laccase Activity ChangesThe changes of AsA content and activity of AO and Laccase in 'Hayward' kiwifruit were studied during the post-harvest storage at 20 ?.The results showed that the contents of AsA was 70.7 mg/100 g,and the contents of AsA decreased 32.74mg/100g in 25 days storage.Laccase enzyme activity increased in first 15 days and then began to decrease,with the highest activity of 48.4U/mL at the fifteenth days of storage.AO activity was changing alternatively with tendency of decreasing-increasing-decreasing.During storage for 15 days,the activity of AO was increased to 2.74U/g FW.