isolated from other species, for example from Petunia [18],
results in tomato plants with higher levels of quercetin
glycosides in their fruit peel. This shows that, when removing
the bottleneck of CHI in the biosynthetic pathway,
flavonoids can be synthesized. It is therefore likely that the
default state for the peel of tomatoes is to produce these
phenolic compounds, as hypothesized [16].
It was also suggested that cultivated tomato might have
lost CHI expression in the fruit peel relatively early during
domestication or even before, given that this trait was
observed in all the cultivars of domesticated tomato analysed,
including S. lycopersicum v. cerasiforme [16]. It is
tempting to speculate that, because the fruit peel of some
wild tomato species and of other Solanaceae (e.g. eggplant
[19] and pepper [20]) can accumulate anthocyanins, other
natural mutations occurred in regulatory and/or structural
genes of the flavonoid biosynthetic pathway, affecting not
only flavonol production but also anthocyanin synthesis in
tomatoes [21]. Certainly, further studies are necessary to
clarify this point.