Manipulation of VvAdh to investigate its function in grape berry development

Grapevine (Vitis vinifera L.) plants were transformed with gene constructs containing a grapevine alcohol dehydrogenase (Adh) cDNA (VvAdh2) coupled in a sense and antisense orientation to the constitutive cauliflower mosaic virus 35S promoter. Compared to controls, ripening fruits from sense transformed plants displayed a significantly higher ADH activity while a lower ADH activity was observed in antisense transformed plants. Fruit with modified ADH levels displayed no significant changes in phenological characteristics, total acidity and refractive index. Berry phenolic compound content was quite similar in all the transformed plants analyzed. However, compared to control fruits, the mDP and the phenolic acid content were significantly lower in mid-ripening fruits over-expressing VvAdh2 (only transiently), and in berries under-expressing VvAdh2. No major changes were observed in free and glycosidically bound volatile compounds between different transformant types. However, the only significant difference observed is the important reduction in benzyl alcohol and 2-phenylethanol in mature berries overexpressing the VvAdh2 construct. These data largely contrast with previous results obtained on leaves from the same Adh transformants and on Adh-transformed fruit from other species. (c) 2007 Elsevier Ireland Ltd. All rights reserved.