Fruit ripening is a maturation process unique to plants, but the biochemical and molecular mechanisms behind this process have not been fully defined. In June Nature Biotechnology, Roshni Mehta and colleagues from USDA-ARS Vegetable Laboratory in Beltsville, US, shows that polyamines have a physiological role in ripening and their accumulation in tomatoes enhances phytonutrient content and juice quality and increases vine life (Nat Biotechnol 2002, 20:613-618).

Mehta et al. expressed a yeast S-adenosylmethionine decarboxylase gene (ySAMdc; Spe2) fused with a ripening-inducible E8 promoter in tomatoes to increase the levels of the polyamines spermidine and spermine during the fruit ripening period. The enhanced expression of the ySAMdc gene caused an increased conversion of putrescine into higher polyamines and thus induced ripening-specific accumulation of spermidine and spermine. This led to an increase in the concentration of lycopene and ethylene, prolonged vine life and enhanced fruit juice quality.

"The enhancement...