Effects Of Ethephon And 1-MCP On The Formation Mechanism Of Aroma Of Jackfruit Fruit

Jackfruit is a typical climacteric fruit.As the fruit matures,the ester aroma increases gradually.AAT(alcohol acyltransferase)is a key enzyme in the synthesis of esters.The post-ripening of jackfruit fruit is very sensitive to ethylene.Exogenous ethephon(ETH)treatment can promote the ripening and senescence of jackfruit fruit,and the ethylene receptor inhibitor 1-methylcyclopropene(1-MCP)significantly prolongs the storage time of jackfruit fruit.In this experiment,'Haida 2' jackfruit was used to be treated with 1000 mg/L ETH and 0.5 mg/L 1-MCP.Their aroma,AAT activities,the expression of AheAAT gene and AheERF1/2 transcription factor and the correlations between AheERF1/2 transcription factor and AheAAT gene were studied.The results were as follows:1.A total of 109 volatile substances were detected in the three treatments of CK,Ethephon and 1-MCP,including 55 esters,14 hydrocarbons,10 alcohols,17 aldehydes,6 ketones and 2 acids.Ethephon treatment increased the type of aroma substances,but reduced the content of aroma substances.1-MCP treatment not only reduced the type of aroma substances but also reduces the aroma substance content.Isoamyl alcohol,isoamyl acetate,butyl acetate,isovaleraldehyde,ethyl isovalerate,ethyl butyrate,and hexanal were the characteristic aroma components common in the three treatments.Principal component analysis showed that ETH treatment improved the aroma quality of jackfruit,while 1-MCP treatment decreased the aroma quality of jackfruit.2.ETH treatment reduced the contents of esters and aldehydes,increased the contents of alcohols and hydrocarbons,decreased the species of aldehydes,increased the species of esters and alcohols,and had little effect on the species of hydrocarbons.1-MCP treatment reduced the content and type of esters,increased the content and type of alcohols and aldehydes,and had little effect on the content and type of hydrocarbons.3.ETH treatment promoted the ripening and senescence of the jackfruit fruit,advanced the time of peak activity of AAT,but reduced the enzyme activity.1-MCP treatment prolonged the storage period of jackfruit fruit,significantly inhibited the activity of AAT in the early stage of post-maturing,and reduced the activity of AAT in the late ripening stage.4.The AAT gene,named AheAAT,was cloned from jackfruit fruit and its full length was 1380 bp,encoding 459 amino acids.AheAAT had a conserved domain H-x-x-x-D and an L-x-x-YYPLAGR active site motif,a D(N)F(V)GWG add-on motif.The AheAAT gene belonged to the BAHD alcohol acyltransferase family.Its amino acid sequence had the highest similarity to apples and pears.AheERF1/2 transcription factor was cloned from the fruit of jackfruit.AheERF1 transcription factor,648 bp in length,encoded 215 amino acids,which had the highest homology with apple and kidney bean.The AheERF2 transcription factor was 657 bp in length and encoded 218 amino acids.Its homology was highest with apple and papaya.The amino acid sequence of AheERF1/2 contained an AP2/ERF conserved sequence consisting of 64/65 amino acid residues and had a characteristic sequence of an ERF family transcription factor.5.The results of real-time PCR showed that the expression trend of AheAAT gene of CK increased first and then decreased.The expression pattern of AheERF1/2 transcription factor was the same as that of AheAAT gene.The expression of AheAAT gene and transcription factor AheERF1/2 was significantly correlated.ETH treatment advanced the expression peak of AheAAT gene and the peak expression of AheERF1/2 transcription factor,down-regulated the expression of AheAAT gene and AheERF1/2 transcription factor,and decreased the correlation between AheAAT gene and AheERF2 transcription factor.1-MCP treatment inhibited the expression of AheAAT gene and AheERF1/2 transcription factor in the early stage of storage,and down-regulated the expression levels of AheAAT gene and AheERF1/2 transcription factor in the late storage stage.However,1-MCP had little effect on the correlation of the AheERF1/2 transcription factor with the AheAAT gene.