| The production process of Gongfu black tea mainly includes: withering,rolling,fermentation,and drying.Among them,withering is the basic process to form the unique quality of Gongfu black tea.At present,research on the optimization of Gongfu black tea withering technology is extensive,but the effect mechanism of low temperature treatment of fresh leaves on black tea quality is not clear.In this paper,fresh samples of one bud and two leaves of Fuding white tea are used as materials.After low temperature treatment,the black tea is processed in accordance with traditional techniques.Observe the changes in the enzyme activity and the contents of the samples during low-temperature treatment,and the changes in gene expression at the transcriptome level during the response of fresh leaves of tea trees to low-temperature stress.Explore the process of Gongfu black tea after low-temperature treatment Quality characteristics and formation mechanism,and the use of exogenous hormone treatment on tea leaves,combined with fluorescent quantitative PCR method to verify the transcriptome sequencing results.The main results are as follows:1.Low temperature treatment can significantly reduce the activity of PPO and POD in fresh leaves,but the enzyme activity is significantly enhanced during processing.After low temperature treatment,the contents of tea polyphenols,catechins and gallic acids in fresh leaves of tea trees increased,and the contents of EGC,EC,EGCG and ECG increased significantly;the contents of tea polyphenols and catechins gradually increased in subsequent processing.Declining trend,while gallic acid is increasing gradually,low temperature treatment will increase such changes.Low temperature treatment will increase the content of theaflavin and its components in withered leaves.Among them,the content of TF and TF-3’-G is 150% and 66.67%higher than that of the control after 8 hours of low temperature treatment;Theaflavins and theaflavin contents were 6.00% and 26.83% higher than the control,respectively.The amino acid content of fresh leaves of tea tree increased after low temperature treatment,among which the content of Glu,Asn,and Thea was significantly higher than that of the control,and the total amino acid content of the samples treated with low temperature during the subsequent processing was higher than that of the control.After the low temperature treatment,the aldehydes and alcohols with floral and fruity aroma in the tea made from fresh leaves increased significantly.Combined with sensory evaluation,low temperature treatment can effectively improve the quality of tea,and the overall quality of the finished tea treated at low temperature for 8 h is better.2.After low temperature treatment of fresh leaves of tea plants,a total of 2060 differential genes were detected in the sample,of which 481 genes were up-regulated and 1579 genes were down-regulated;the genes that significantly changed at the transcriptome level were mainly concentrated in nucleic acid regulation and protein transcription During the response of factors and hormones,the genes involved in tea plant hormone signal transduction,mitogen-activated protein kinase signaling pathway,and pathogen-bacteria interaction are more varied.After 16 hours of withering,there were 1358 differential genes,of which 752 genes were up-regulated and 606 genes were down-regulated.Gene expression at the transcriptome level not only changed significantly in basic metabolism such as photosynthesis,but also oxidized,Flavonoids,amino acids and linoleic acid metabolism pathways are more active3.In order to study the effect of low temperature treatment on the quality of fresh tea leaves and finished tea,this study extracted total RNA from fresh leaf samples and untreated control samples after 8 h of low temperature treatment,and performed transcriptome sequencing analysis.The results showed that after low temperature treatment,the expression of genes in fresh leaves of tea trees was very active in response to low temperature stress.Compared with control samples,a total of 2060 differential genes were detected in the 8h sample after low temperature treatment,of which 481 genes were up-regulated 1579 genes are down-regulated;genes that have undergone significant changes at the transcriptome level are mainly concentrated in the regulation of nucleic acids,protein transcription factors and hormone response processes,and are involved in tea plant hormone signalling,mitogen-activated protein kinase signaling pathways,and Genes related to the interaction of pathogenic bacteria have many changes.After 16 hours of withering,compared with the control,there were a total of 1358 differential genes,of which 752 genes were up-regulated and 606 genes were down-regulated;gene expression at the transcriptome level not only changed significantly in basic metabolism such as photosynthesis,It is also active in oxidation,flavonoids,amino acids,and linoleic acid metabolism pathways.4.Compared with the control sample,28 and 15 differentially expressed genes were significantly enriched in the metabolic pathways and amino acid biosynthetic pathways related to flavonoid metabolism after low temperature treatment,of which the flavonoid and tea Differential genes that were significantly positively correlated with amino acids were down-regulated,and the total amount of catechin and free amino groups in the samples after low temperature treatment increased.After continued to wither for 16 h,genes involved in catechin synthesis in the flavonoid pathway were up-regulated;genes that were positively associated with EGCG in the amino acid biosynthesis pathway were down-regulated,and genes that were significantly negatively related to theanine were down-regulated,and The content of EGCG in the sample was lower than that of the control,and the content of theanine was significantly higher than that of the control.In addition,low temperature treatment resulted in enhanced terpene biosynthesis,α-linolenic acid metabolism and fatty acid degradation,which caused changes in the total and amount of volatile compounds in tea.Therefore,low temperature treatment will cause significant changes in gene transcription and content of tea flavor compounds,thereby promoting the special flavor of various teas.5.Low temperature treatment of fresh tea leaves will cause the differential expression of genes in the phytohormone conduction pathway in tea,thereby regulating the material metabolism of tea,using exogenous hormone treatment to simulate the hormone metabolism regulation pathway shown in the transcriptome sequencing results,which can effectively Verify transcriptome sequencing results... |
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