Different Roles of the Five Alcohol Acyltransferases in Peach Fruit Aroma Development

Peach (Prunus persica) fruit emit more than 100 volatile organic compounds. Among these volatiles, gamma-decalactone is the key compound that contributes to peach aroma. The final step in lactones biosynthesis is catalyzed by alcohol acyltransferases (AATs). In this study, five AAT genes were isolated in the peach genome, and the ways that these genes contribute toward the peach aroma were studied. The sequence analysis of the five AATs showed PpAAT4 and PpAAT5 are truncated genes, missing important residues such as HXXXD. The expressions of PpAATs were investigated to identify the roles in creating the peach aroma. The results indicated that only PpAAT1 is highly expressed during gamma-decalactone formation. A functional survey of the five PpAATs, using the oleaginous yeast expression system, suggested that only PpAAT1 significantly increased the gamma-decalactone content, whereas the other four PpAATs did not significantly alter the gamma-decalactone content. Enzyme assays on PpAATs heterologously expressed and purified from Escherichia coli indicated that only PpAAT1 could catalyze the formation of gamma-decalactone. All results indicated that PpAAT1 is a more efficient enzyme than the other four PpAATs during the gamma-decalactone biosynthesis process in peach fruit. The results from this study should help improve peach fruit aroma.