Flavonoid profiling and biosynthetic gene expression in flesh and peel of two tomato genotypes grown under UV-B-depleted conditions during ripening

The aim of this study was to evaluate the effect of shielding solar ultraviolet B radiation on the accumulation of some flavonoids and their precursors hydroxycinnamic acids in tomato (Solanum lycopersicum) using LC-ESI-MS/MS. In particular, flesh and peel of two tomato hybrids, DRW 5981 and Esperanza, were separately analysed. The hybrids have been chosen on account of their different response to the light, since it was previously reported that they show a different pigmentation and an opposite behaviour under UV-B in terms of carotenoids and ascorbic acid content at different ripening stages. To determine the effect of UV-B radiation during tomato ripening, we also measured the expression of some flavonoid biosynthetic genes by Real Time RT-PCR analysis. The results here presented allowed us to conclude that UV-B radiation deeply and differentially affect the content of the considered flavonoids and hydroxycinnamic acids as well as the expression of some of their biosynthetic genes in both flesh and peel during the ripening process. On the other hand, the collected data clearly showed that this influence varies between different genotypes. We conclude that the use of specific plastic covers able to eliminate UV-B radiation may be an environmental-friendly approach to modulate the expression of structural genes and, in turn, to enhance healthy antioxidant compounds in fruits of specific tomato cultivars.