OTAIZA GONZÁLEZ SANTIAGO NICOLÁS
Congresos y reuniones científicas
Título:
Understanding the regulations of vitamin E biosynthesis in tomato fruits.
Reunión:
Congreso; Plant Metabolic Engineering; 2011
Institución organizadora:
Gordon Reserch Conference
Resumen:
Understanding of metabolic pathways regulation in plants is of fundamental importance
especially for the biosynthesis of essential compounds for human diets. Although
tomato fruits are important sources of vitamin E neither the genetic determinants of its
contents nor the regulation of its biosynthesis are currently understood in this species.
We present here results from the analyses of QTL for tocopherol contents in mature
fruits previously identified in an introgression line (IL) population derived from an
interspecific cross harboring wild alleles. Fine mapping of two of these QTL allowed to
identify three vte loci (vte1, vte3 and vte4) encoding enzymes of the last steps in
vitamin E synthesis in plants. Expression profiles of these genes showed their
expression pattern in source and sink leaves and also across fruit development. Fruit
silencing of vte4 gene resulted in reduced levels of α- and β-tocopherol and a
consequent accumulation of γ-tocopherol both in mature green and ripe tomatoes. By
other hand, the reduction of the vte3 mRNA resulted in significant increases of β-
tocopherol both at mature green and ripe stages. However, at this later stage γ-
tocopherol levels resulted also significantly reduced. Vte1 gene was not sensitive to
silencing by this system. These results suggest that other unknown mechanism could
be operating in the regulation of this enzymatic step catalyzed by VTE1 and also that a
different regulatory role of VTE3 enzyme exists with regards to the maturation stage of
the fruits. Moreover, detailed metabolite profiles of silenced fruits showed that
alterations in tocopherol levels correlated with massive increases in the concentrations
of the photorespiratory intermediate glycine (~ 4 folds) and the levels of leucine (~ 3
folds) in ripe fruits. These changes were accompanied by increments in the levels of
the pigments carotenes and lycopene, suggesting that both tocopherol and carotenoid
pathways are co-regulated. Moreover, vte4 silencing was accompanied by increments
in antioxidant capacity in green and ripe tomatoes, while the silencing of vte3 resulted
in increased antioxidant levels in ripe fruits. These results suggest that tocopherol
composition may regulate the pigment accumulation and the cellular redox state of the
tomato fruit