Vitamin E biosynthesis is transcriptionally regulated determining the cellular redox state in tomato

QUADRANA L; ALMEIDA J; OTAIZA S; DE GODOY F; ASIS R; ROSSI MM; CARRARI F

Potrero de los Funes, San Luis.

Congreso; XLVII Reunión Anual Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2011

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

Tocopherols are a group amphiphilic antioxidants belonging to the vitamin E (VTE) family. Although tomato fruits are important sources of VTE, its biosynthesis has been scarcely studied. To understand the VTE metabolism in tomato, we analyzed the expression of 47 enzymes encoding genes involved in the biosynthetic pathway of VTE in different tomato tissues by a dedicated qRT-PCRarray which covered all enzymes of the VTE biosynthetic pathway and the two convergent methylerythritol phosphate (MEP) and shikimate (SK) pathways. Results showed that most of the analyzed genes of the VTE core-pathway are differentially expressed in fruits and source and sink leaves and that their expression levels decrease along fruit ripening. Except for few examples, the same is true for the MEP and SK pathways genes. These results suggest that VTE biosynthesis might be regulated at the level of transcription of the intervening enzymes but this regulation operates in photosynthetic tissues, mainly in leaves and at very earlier stages of fruit development. Silencing of vte3(1) gene in tomato fruits by VIGS resulted in significant increases of b-tocopherol and reduced levels of g-tocopherol. On the other hand, vte4 gene silencing resulted in reduced levels of a-and b-tocopherol and accumulation of g-tocopherol. Moreover, detailed metabolite profiles of the silenced fruits showed that alterations in tocopherol levels correlated with massive increases in the photorespiratory intermediate glycine and the levels of leucine as well as with a significant reduction in lipids contents. These changes were accompanied by increments in carotenes, lycopene and antioxidant capacity, suggesting that both tocopherol and carotenoid pathways are co-regulated resulting in the regulation of the cellular redox state of the tomato fruits.