Variations Of Characteristic Compounds In Grafting Of Tea Cultivar 'Xianghongdian No.1'

Tea,which contains the characteristic compounds such as theanine,caffeine and tea polyphenols,is one of the most widely consumed non-alcoholic beverages in the world.However,there are many problems in early tea gardens in China,such as mixed varieties and low yield per unit area.Aiming at this phenomenon,it is possible to efficiently update the varieties of low-yielding tea gardens through grafting technology which is more practical in tea garden completed and lower cost compared with the other technology of re-planting tea seedlings.However,what is the biological basis of tea plant grafting for the improvement of tea varieties?Does the interaction between rootstock and scion cause changes in the characteristic compounds of tea?This study used the fine variety of tea cultivar‘Xianghongdian No.1'selected from Jinzhai as scion to carry out the grafting of the tea plants‘Qimenzhong'in the local old tea garden.Then,Grafting leaf,Rootstock leaf and Scion leaf were collected for characteristic compounds analysis and transcriptome sequencing,respectively.To study the variations of characteristic compounds in grafting of tea plants and the transcriptional regulation of related genes in the biosynthesis process.The main results were shown as follows:1.Through the detection of characteristic compounds,we found that the content of caffeine and total catechins were the highest in Grafting leaf,followed by Scion leaf and Rootstock leaf.While,the content of theanine was the highest in Scion leaf,followed by Rootstock leaf,and the lowest in Grafting leaf.2.A total of 59.31 Gb clean data was obtained from transcriptome sequencing.The average mapping rate with the tea tree reference genome was 73.04%,and 42,765 genes were detected.Among them,there were 11,041 differentially expressed genes(DEGs)among three comparison comparisons.3.All DEGs were enriched in KEGG Pathway,and the common pathways of "flavone and flavonol biosynthesis","biosynthesis of secondary metabolites" and "Terpenoid backbone biosynthesis" were significantly enriched in the Rootstock leaf-vs-Grafting leaf comparison comparisons.Total of 23 randomly selected DEGs were verified by qRT-PCR,and the expression patterns of 20 of them(87%)were consistent with the trend of RNA-Seq.4.Analysis of the differential expression of characteristic compounds biosynthesis related genes in tea plants,we found that the expression level of genes involved in the biosynthesis of theanine in Grafting leaf was lower than that of Rootstock leaf,Conversely,the level of genes expression associated with caffeine and catechins biosynthesis in Grafting leaf were higher.5.Construct the co-expression network analysis between 2634 TFs genes were identified by RNA-Seq and all genes related to the characteristic compounds biosynthesis in tea plants.The candidate transcription factors regulating the genes involved in the synthesis of theanine,caffeine and catechins in tea plants were predicted.This lays the foundation for studying the transcriptional regulation mechanism of target genes.