Forschungs- & Entwicklungsinformationsdienst der Gemeinschaft - CORDIS

Improving tomato fruit quality

We have investigated the role of photoreceptors such as phytochrome on the fruit-ripening process, with the objective of increasing tomato fruit quality. We have generated a series of phytochrome- and cryptochrome-deficient tomato mutants and have crossed them to make a range of different double, triple, and quadruple mutants. Many of these have very clear and dramatic effects on truss and fruit development. These have been the focus for assessing the role of individual photoreceptors in the fruit ripening process. We have grown these mutants in the greenhouse in Spain and have performed a series of analyses to look at general properties such as brix, viscosity, firmness, etc. In parallel these mutants have been grown under greenhouse conditions in Italy and RNA has been prepared from fruits harvested throughout the ripening process and used for cDNA-AFLP to identify differentially expressed genes.

We have focused on the manipulation of key light signalling molecules. One objective was the isolation of constitutively photomorphogenic mutants in tomato. For this, we screened several thousand mutagenized seedlings in darkness. This approach was very successful and a range of new light signal transduction mutants with constitutive photomorphogenic phenotypes in darkness have been obtained. At least one of these is likely to be a null mutation in the tomato DET1 gene. A second objective has been the isolation of ATROVIOLACEA (ATV), DARK GREEN (DG), ANTHOCYANIN FRUIT (AF) and/or PUNCTATE (PN) genes from their respective mutants. We have performed basic physiological characterization of these mutants, which has been extended to photobiology experiments. These physiological characterizations have revealed that ATV and AF are the most interesting genes that warrant cloning. Most pogress has been made with ATV, which has been mapped to a small region on the long arm of chromosome 7. When combined, the atv and Af mutations result in fruits with extremely high levels of anthocyanins. Such a new kind of tomato fruit could be very interesting as a functional food, given the strong antioxidant activity of these compounds. A final objective involved the generation of tomato plants containing light hypersensitive versions of key light signalling intermediates such as DET1, COP1 and HY5. Most interestingly, DET1 has been suppressed specifically in fruits using fruit-specific promoters and RNA interference constructs, which resulted in the generation of normal healthy plants that produced fruits with significantly enhanced carotenoid and flavonoid contents.

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Reported by

Stazione Zoologica
Stazione Zoologica, Laboratory of Cell Signalling
I 80121 Naples
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