Overexpression of petunia chalcone isomerase in tomato results in fruit containing increased levels of flavonols

Tomatoes are an excellent source of the carotenoid lycopene, a compound tha t is thought to be protective against prostate cancer. They also contain sm all amounts of flavonoids in their peel (similar to5-10 mg/kg fresh weight) , mainly naringenin chalcone and the flavonol rutin, a quercetin glycoside. Flavonols are very potent antioxidants, and an increasing body of epidemio logical data suggests that high flavonoid intake is correlated with a decre ased risk for cardiovascular disease. We have upregulated flavonol biosynth esis in the tomato in order to generate fruit with increased antioxidant ca pacity and a wider range of potential health benefit properties. This invol ved transformation of tomato with the Petunia chi-a gene encoding chalcone isomerase. Resulting transgenic tomato lines produced an increase of up to 78 fold in fruit peel flavonols, mainly due to an accumulation of rutin. No gross phenotypical differences were observed between high-flavonol transge nic and control lines. The phenotype segregated with the transgene and demo nstrated a stable inheritance pattern over four subsequent generations test ed thus far. Whole-fruit flavonol levels in the best of these lines are sim ilar to those found in onions, a crop with naturally high levels of flavono l compounds. Processing of high-flavonol tomatoes demonstrated that 65% of flavonols present in the fresh fruit were retained in the processed paste, supporting their potential as raw materials for tomato-based functional foo d products.