Expression of genes associated with anthocyanin synthesis in red-purplish, pink, pinkish-green and green grape berries from mutated 'Sangiovese' biotypes: A case study

Using normal red-purplish grape bunches and pink, pink-green and green berry colour-mutated biotypes of cv. Sangiovese (V. vinifera L.), we investigated their anthocyanin metabolism via biochemical and molecular assays. The number and composition of the different types of anthocyanins were analysed by spectrophotometry and chromatography. The expression of six structural genes of the biosynthetic pathway (chalcone synthase [CHS], chalcone isomerase [CHI], flavanon-3-hydroxylase [F3H], dihydroflavonol 4-reductase [DFR], leucoanthocyanidin dioxygenase [LDOX] and UDP-glucose 3-O-flavonoid:glucosyltransferase [UFGT]) was determined over the four weeks subsequent to veraison via Northen blot and Real Time PCR.The grapes from the non-mutated biotype showed a prevailing accumulation of monoglycoside anthocyanin fractions, with only traces of acetyl and p-coumaroyl derivatives. The berries of the mutated biotypes showed a gradual berry pigment loss associated with a reduction in total anthocyanin content, although anthocyanin composition was the same of the non-mutant biotype. Indeed, the Northern blot assay data, as confirmed by the quantitative Real Time PCR tests, showed a differential expression in the berries of the non mutated and mutated biotypes for the UFGT gene, proving normal in the red-purplish, lower in the biotypes with pink and pink-green berries and wholly lacking in the green one. Thus, the UFGT gene in berry skin of colour-mutated 'Sangiovese' biotypes is controlled independently of the other structural genes encoding enzymes in the anthocyanin biosynthetic pathway and its capacity of expression is a critical factor in the synthesis and storage of these compounds.