Fig. 7

Expression profile of VviGRFs during grape berry ripening. (a) Expression pattern of VviGRFs in five grape varieties during berry developmental stages. The used grape berries were taken from five red-skin grape varieties, namely, Sangiovese (S.), Barbera (B.), Negro amaro (N.), Refosco (R.), and Primitivo (P.). Berries were collected at four phenological stages, as follows: pea-sized berries at 20 days after flowering (Pea), berries beginning to touch just prior to veraison (Touch), softening berries at the end of veraison (Soft), and berries ripe for harvest (Harv) [36]. The obtained data were processed using log2 normalization. The colour scale represents relative expression levels. (b) qRT-PCR results of eight VviGRF genes during berry ripening. As previous study indicated [38], EL33, EL35 and EL37 represent three important stages during berry ripening, respectively. EL33 means the stage when berries are still hard and green, EL35 means the veraison when berries begin to colour and enlarge, and EL37 presents the period when berries will mature soon but not quite ripe. Pea, touch, soft and harvest stages in a correspond to EL31, EL34, EL37 and EL38, respectively. Period before veraison is named the early stage in this study, and the period after veraion is the late stage. Thus EL33, pea, touch belong to the early stages, and EL37, soft, harvest belong to the late stage. Expression data was normalized to VviActin gene expression level, and every VviGRFs at EL33 stage was normalized as “1”. The mean expression value was calculated from three replications. Vertical bars indicate the standard error of mean. **P < 0.01 and *P < 0.05 compared with expression level at EL33 stage