Metabolic engineering of beta-carotene and lycopene content in tomato fruit

Ripe tomato fruits accumulate large amounts of the red linear carotene, lyc opene (a dietary antioxidant) and small amounts of its orange cyclisation p roduct, beta-carotene (pro-vitamin A). Lycopene is transformed into beta-ca rotene by the action of lycopene beta-cyclase (beta -Lcy). We introduced, v ia Agrobacterium-mediated transformation, DNA constructs aimed at up-regula ting (OE construct) or down-regulating (AS construct) the expression of the beta -Lcy gene in a fruit-specific fashion. Three transformants containing the OE construct show a significant Increase in fruit beta-carotene conten t. The fruits from these plants display different colour phenotypes, from o range to orange-red, depending on the lycopene/beta-carotene ratio. Fruits from AS transformants show up to 50% inhibition of beta -Lcy expression, ac companied by a slight increase in lycopene content. Leaf carotenoid composi tion is unaltered in all transformants. In most transformants, an increase in total carotenoid content is observed with respect to the parental line. This increase occurs in the absence of major variations in the expression o f endogenous carotenoid genes.