Transformation Of Ester Aroma And Function Analysis Of Key Biosynthesis Enzymes Involved In Their Formation During Tea Withering

Aroma is one of the key factors of the tea quality.Ester aroma has flowery and fruity aroma,which plays an important role in of tea aroma quality.Tea processing,especially withering,can significantly affect the accumulation of ester aroma.However,up to now,the transformation of ester aroma compounds during tea withering process and the underlying molecular mechanism are still unclear.In this study,the transformation rule of ester aroma during tea withering was studied using oolong tea.Combined with metabolism and transcription analysis,the synthesis regulation network of main ester aroma was established.On this basis,the synthesis mechanism of several important ester aroma compounds was preliminarily revealed.The main results are as follows:1.The changes of aroma compounds in oolong tea processing were analyzed by targeted metabolism analysis.It was found that withering process could significantly affect the accumulation of aroma substances,especially ester aroma and aroma precursors.For example,the content of phenylethanol increased from 13.75% to 27.36%,geraniol increased from 11.87% to 22.34%,nerolidol increased from 13.62% to 69.04%,and the contents of benzyl alcohol,and benzyl alcohol and linalyl acetate also increased;2.SPME-GC-MS was used to detect the changes of ester aroma in different withering time.The results showed that the contents of(E)-butyrate-3-hexenyl acetate,cis-3-hexene acetate,isobutyl acetate,phenylethyl acetate,benzyl acetate,citronellyl acetate,nerolin acetate and geranyl acetate decreased at first and then increased during the withering process;3.RNA Seq technology was used to detect the gene expression of tea leaves at different withering time.The regulation network of tea ester aroma synthesis was constructed through the combined analysis of transcriptome and ester aroma compounds,and 42 genes related to ester aroma synthesis were screened out.Among them,TEA011042,TEA03580,TEA02998,TEA020999,TEA013065 and TEA006263 may participate in the synthesis of tea ester aroma during withering;4.The results of prokaryotic expression showed that tea Cs AAT1 had the highest catalytic activity for citronellol,Cs AAT2 for benzyl alcohol and phenethyl alcohol,Cs AAT3 for geraniol and nerol and Cs AAT4 for octanol.On this basis,the mechanism of Cs AAT1-4 in tea plant aroma synthesis was preliminarily revealed by combining tobacco and tea genetic transformation systems.