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There is a growing interest in producing food plants with increased amounts of antioxidants because of their potential health benefits. Polyphenolic secondary metabolites, such as flavonoids and stilbenes, have been investigated for their significant antioxidant activity, important both for plant physiology and human nutrition. With the aim to verify whether the synthesis of resveratrol in tomato fruit affected the redox status of transformed tomato tissues, in the present work we took advantage of the availability of two different transgenic tomato lines in which a grape stilbene synthase gene was expressed under a constitutive or a tissue specific promoter, respectively. The induction of resveratrol synthesis in tomato affected the redox status of transformed tomato fruit. In particular, ascorbate and glutathione pool increased, significantly and proportionally to the amount of the resveratrol synthesised in transformed tissues. Noteworthy, the increase in ascorbate and glutathione pool paralleled with a significant increase in the activities of the main enzymes involved in redox homeostasis, i.e. catalase, ascorbate peroxidase as well the enzymes responsive for ascorbate recycling. Furthermore, lipoxygenase activity and levels of polyunsaturated fatty acids hydroperoxides, were reduced in fruit tissues from transgenic tomato lines. The synthesis of resveratrol, together with the global redox status had an impact on the total antioxidant activity of transgenic fruits. Again the total antioxidant capability increased proportionally to the amount of synthesised resveratrol with the most remarkable increase recorded from the lipophilic-resveratrol containing-fraction of transgenic fruits. Overall, our results pointed a higher nutritional value of resveratrol synthesizing tomato fruits.
Published Date: 2013-04-10; Received Date: 2013-02-11