Regulator genes offer the advantage of upregulating many genes at once along the flavonoid pathway (Bren 2003). Butelli (2008) reported that the expression of Del/Ros upregulates PAL, CHI, and
F3H. PAL determines the flavonoid flux and may explain the
increase in flavonol content in both the peel and the flesh beyond
the elevated anthocyanin content. The upregulation of DFR
(dihydroflavonol reductase) affects the distribution of flavonol and
anthocyanin content (Kim and others 2004a). Even though Butelli
and others (2008) reported the Del/Ros1 upregulated DFR, the
effect may not have been strong enough to use all the flavonol flux
that is necessary to convert to anthocyanin.