Study On The Synthesis Of Characteristic Aroma-2-phenylethanol In Vidal Grape At Ripping And After-ripping

2-phenylethanol is an important aroma compounds,with a pleasant fruity aroma and honey aroma.lt is an important and characteristic aroma in Vidal grape.Phenylalanine as precursors of volatile phenols,is the source of 2-phenylethanol in grape。Aromatic amino acid decarboxylase Catalyzed the first step reaction in the synthesis of 2 Phenylethanol,also,a key enzyme.People can utilize enzymatic gene expression to control 2 - phenylethanol biosynthesis.In this paper,a fragment of the aromatic amino acid decarboxylase cDNA was cloned from the grapes through e-splicing,PCR methods.And also,this paper studied in the expression of aromatic amino acid decarboxylase at the stages of ripening and after-ripening in Vidal grapes.These results provide a substantial base for the further research concerning 2-Phenylethanol metabolic pathway.(1) A grape segment aromatic amino acid decarboxylase gene sequences(832 bp) was cloned by polymerase chain reaction(PCR),then introduced it into the plasmid pMD19-T and transferred into E. coli.DH5α.After screening by blue and white dot from host cell,the plasmid DNA was extracted and then sequenced.The vector contained a segment aromatic amino acid decarboxylase gene.(2)The changes of AADC gene expression at transcriptional levels and production levels were analyzed in the period of ripening to and after-ripening Vidal grape berries by means of RT-PCR.The results showed that a increased continuously AADC fragments gene transcripts of the overall trends, and amino acid automatic analyzer test results showed that in ripening and after-ripening period of Vidal grapes,phenylalanine as precursors was a large number of accumulation;HPLC test results showed that phenylethylamine in the ripening is increasing,then the content reached the maximum after-flowering 130 days.The content reached 0.0195mg/kg,after rapidly reduced.(3)Unsaturated fatty acids and polyamines were Response Factors under the Stress.The maximum of unsaturated fatty acid in Vidal grape ripening reached after-flowering 120 days,reached 0.195mg/kg, then,decreased.After-flowering 160 days it reached another peak concentration,followed by a slow change;The content of spennine reached peak content at after-flowering 110 days,0.058mg/kg,then,decreased.The content of spermidine increased and reached the peak at 0.113mg/kg after-flowering 140 days,then,sharply declined.