Effect On Secondary Metabolites In Tea Leaves Induced By Exogenous Methyl Jasmonate

Methyl jasmonate(MeJA) which is an effective exogenous elicitor could be hydrolyzed intojasmonate acid after entering plants, then form jasmonate acid-amino acid conjunction, and finanllymake an impact on secondary metabolites. Tea leaves contain a variety of secondary metabolites, andthese compounds could ensure the quality of made tea to some degree. In this study, we carried outmethod of GC-MS, HPLC, and qRT-PCR in analyzing changes of secondary metabolites in tea leavestreated with MeJA.This study could be helpful to figure out the effect of MeJA on secondarymetabolites in tea leave, and could provide a theoretical basis and technical support for applying MeJAto enhance the quality of tea leaves.The main results were as follows:1. HS-SPME and DE were carried out to analyze changes of volatile compounds in MeJA-treatedtea leaves comparatively.①HS–SPME was applied in volatile enrichment of the freeze-dried tea leaves,then qualitatively analyzing volatile compounds combinig GC-MS. Results showed that the relativecontent of some29volatile compounds increased significantly in MeJA-treated tea leaves, especiallyafter24h treatment by MeJA, compared to the MeJA-untreated tea leaves, it increased by23.79%whichreached a significant difference (**p<0.01). The relative contant of β-Linalool increased from30.87%to37.92%, linalool oxides II increased from6.08%to9.18%, and nerolidol increased from1.55%to4.45%.②Volatile compounds in tea leaves was also enriched through DE, and analyzed by GC-MSqualitatively and quantitatively. Compared to MeJA-untreated tea leaves, the content of some26volatilecompounds in MeJA-treated tea leaves increased obviously. Especially after24h treatment, the totalcontent of volatile compounds was increased by69.6%. This method could enrich most of the lowboiling point volatile compounds, such as alcoholic volatile compounds and hydrocarbon, during thetreatment, the content of cis-3-hexenol increased from5.72μg/g to9.74μg/g, and the content oftrans-3-hexenol increased from3.9μg/g to6.97μg/g, the difference was extremely significant(**p<0.01). Moreover, the content of β-Linalool increased from2.31μg/g to3.56μg/g.2. The total content of catechins increased significantly after36h treatment by MeJA(**p<0.01),especially the content of EGCG increased by42.06%which also reached a significant level(**p<0.01).Meanwhile, the content of caffeine in tea leaves decreased by2.03mg/g. The content of amino acid inMeJA-treated tea leaves behaves a downward trend along the MeJA treatment procedure. The content oftheanine increased to1218.81mg/100g, nearly the same as the MeJA-untreated tea leaves, during thefirst12hrs after MeJA treatment, then the content of theanine decreased rapidly in successive60hrs, andit fell to625.89mg/100g after72h treatment which behaved a23.94%decrease. During the treatmentprocedure, the content of isoleucine keep decreasing, it decreased by32.03%compared toMeJA-untreated ones after72h treatment(**p<0.01).3. The gene expression of β-primeverosidase was up-regulated by230%compared to theMeJA-untreated tea leaves within24h treatment, and the gene expression of polyphenol was up-regulated by100%, howerve the gene expression of β-glycosidase was suppressed to a half level.The activities of polyphenol oxidase and β-glucosidase in fresh tea leaves changed after the MeJAtreatment. It is noting that the activity of β-glucosidase decreased by16%, while the activity ofpolyphenol oxidase increased by17%.