Expression of genes associated with anthocyanin synthesis in grape berries from mutated cv. Sangiovese biotypes.

摘要

Using normal, i.e. dark red-purplish grape bunches (SG), and colour-mutated, i.e. greyish, greyish pink, pink and yellow-green clusters, biotypes of cv. Sangiovese (SGM), we investigated anthocyanin metabolism via biochemical and molecular assays to determine the main structural genes as they are expressed along the biosynthetic pathway of these compounds. The number and composition of the different types of anthocyanins were analysed by chromatography and spectrophotometry. The expression of six structural genes, i.e. chalcone synthase (CHS) [naringenin-chalcone synthase], chalcone isomerase (CHI), leucoanthocyanidin dioxygenase (LDOX) [leucocyanidin oxygenase] and UDPglucosio-flavonoid 3-o-glucosil transferase (UFGT), was determined over the four weeks subsequent to veraison via northern blot and Real Time PCR. The normal SG grapes showed a prevailing storage of monoglycoside anthocyanin fractions, colour-mutated SGM biotypes showed a gradual berry pigment loss associated composition was unchanged. The finding suggests that what varies is not the mechanism controlling anthocyanin synthesis in the mutated biotypes, which capacity to express these traits through the proteins constituting the specific "transcription factors". Indeed, the northern blot assay data, as confirmed by the quantitative Real Time PCR tests, showed a differential expression in the two biotype groups for the UFGT gene, proving normal in the SG, lower in the pink-grey and pink SGM and wholly lacking in the de-pigmented SGM. Thus, the UFGT gene in berry skin is controlled independently of the other structural genes encoding enzymes in the anthocyanin biosynthetic pathway and its capacity of expression, a critical factor in the synthesis and storage of these compounds, can be altered by mutagenesis events..