Antisense suppression of alcohol acetyltransferase gene in ripening melon fruit alters volatile composition

Abstract

Volatile esters are characteristic aroma components of melon (Cucumis melo L.) fruit. Alcohol acetyltransferase (AAT) (EC2.3.1.84) catalyzes the reactions of aliphatic and aromatic alcohols to their esters in the presence of acyl CoA in fruit and flowers. In this study, melon plants were transformed with a gene construct containing a melon AAT cDNA (AAT2) in an antisense orientation, driven by the constructive cauliflower mosaic virus 35S promoter, by ovary-injection transformation method. The transformed plants displayed a range of decreased AAT activities in the ripening fruit. The relative content of volatile esters was reduced, and the average relative content in the transgenic fruit was 78% of the wild-type fruit. However, the relative contents of aldehydes and alcohols increased; the average relative contents were 3.2 times and 2.4 times of those in the wild-type fruit, respectively. Apart from the difference in the volatile compounds, no other phenotypic alterations were noted, including other quality indices, such as the sugar, vitamin C and carotenoid contents. Our study indicates that AAT plays the key role in volatile ester formation in melon fruit.