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Transgenic tomato plants characterized by expression of two transcription factors, Del and Ros, leading to high-flavonoid tomato fruits

Transgenic tomato lines expressing the regulatory proteins (transcription factors) Rosea1 and Delila (from Antirrhinum majus) specifically in ripening fruit. The initial lines produced were in MicroTom. The fruits express high levels of all the genes committed to anthocyanin biosynthesis (including transporters and genes encoding enzymes) as demonstrated by suppression subtraction hybridisation and analysis using the custom microarray developed by PRI Wageningen. They produce on average 1mg per gram fresh weight anthocyanins, which are principally delphinidin 5-glucoside (p-coumaroyl) rutinoside and petunidin 5-glucoside (p-coumaroyl) rutinoside, as confirmed by LC/MS. There arrre also increases in other phenolics(soluble) which are currently being identified. There is an overall increase in flavonoid content of at least 150-fold, and anthocyanins are produced throughout the flesh of the fruit as well as in the skin. There is a significant increase in anti-oxidant capacity as determined by the TEAC assay. This shows that the antioxidant capacity increases about 3-fold in the soluble (hydrophillic) fraction, whereas the antioxidant capacity of the hydrophobic fraction remains unaltered.

The High Anthocyanin (purple) trait has been introduced into two commercial tomato backgrounds - Money Maker and Alisa Craig. The trait is fully heritable in a Mendelian fashion.

These results have been described at 8 pleanary/keynote addresses at prestigous scientific meetings:

Key Innovative Features:
This is the first time that high levels of anthocyanins have been produced in tomato fruit. This trait is restricted to the fruit so that growth and yield are not impaired. These lines have significantly increased antioxidant capacities. The fruit also have significantly improved textural properties and shelf life.

Current Status:
We are introducing this trait into other tomato lines; specifically lines mutant in the enzyme DFR such that high levels of flavonols can be engineered in tomato fruit. We are investigating the basis for the improved textural properties and shelf life of the transgenic lines.

Use of the result and its expected benefits:
We hope that the lines we have produced will provide the material for breeding tomatoes with increased levels of health-promoting flavonoids. The feeding trials performed under PROFOOD with Caenorhabditis elegans showed no effects but are difficult to interpret with respect to health benefits in human. We have prepared large quantites of the tomatoes for mouse feeding studies to be performed on 3 models of disease (Cardio-vascular disease, Cancer and Age-related degeneration). Inclusion of control and purple tomatoes in the diet will allow tests on effects in disease progression, and cellular markers for disease. These analyses are being conducted in collaboration with clinicians and epidemiologists under the sponsorship of an EU-FP6 STReP project, FLORA.

Reported by

John Innes Centre
Department of Cell and Developmental Biology, John Innes Centre
NR4 7UH Norwich
United Kingdom
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