Isolation and Analysis of Anthocyanin Pathway Genes from Ribes Genus Reveals MYB Gene with Potent Anthocyanin-Inducing Capabilities

Horticultural crops of the Ribes genus are valued for their anthocyanin-rich fruits, but until now, there were no data about the genes and regulation of their flavonoid pathway. In this study, the coding sequences of flavonoid pathway enzymes and their putative regulators MYB10, bHLH3 and WD40 were isolated, and their expression analyzed in fruits with varying anthocyanin levels from different cultivars of four species belonging to the Ribes genus. Transcription levels of anthocyanin synthesis enzymes and the regulatory gene RrMYB10 correlated with fruit coloration and anthocyanin quantities of different Ribes cultivars. Regulatory genes were tested for the ability to modulate anthocyanin biosynthesis during transient expression in the leaves of two Nicotiana species and to activate Prunus avium promoters of late anthocyanin biosynthesis genes in N. tabacum. Functional tests showed a strong capability of RrMyb10 to induce anthocyanin synthesis in a heterologous system, even without the concurrent expression of any heterologous bHLH, whereas RrbHLH3 enhanced MYB-induced anthocyanin synthesis. Data obtained in this work facilitate further analysis of the anthocyanin synthesis pathway in key Ribes species, and potent anthocyanin inducer RrMyb10 can be used to manipulate anthocyanin expression in heterologous systems.

Expression and Anthocyanin Biosynthesis-Modulating Potential of Sweet Cherry (Prunus avium L.) MYB10 and bHLH Genes

Anthocyanins are essential contributors to fruit coloration, an important quality feature and a breed determining trait of a sweet cherry fruit. It is well established that the biosynthesis of anthocyanins is regulated by an interplay of specific transcription factors belonging to MYB and bHLH families accompanied by a WD40 protein. In this study, we isolated and analyzed PaWD40, PabHLH3, PabHLH33, and several closely related MYB10 gene variants from different cultivars of sweet cherry, analyzed their expression in fruits with different anthocyanin levels at several developmental stages, and determined their capabilities to modulate anthocyanin synthesis in leaves of two Nicotiana species. Our results indicate that transcription level of variant PaMYB10.1-1 correlates with fruit coloration, but anthocyanin synthesis in Nicotiana was induced by another variant, PaMYB10.1-3, which is moderately expressed in fruits. The analysis of two fruit-expressed bHLH genes revealed that PabHLH3 enhances MYB-induced anthocyanin synthesis, whereas PabHLH33 has strong inhibitory properties.

Phenolics, antioxidative activity and characterization of anthocyanins in berries of blackcurrant interspecific hybrids

The interest in phenols and anthocyanins has increased due to their antioxidant properties and to their potential usage as dietary antioxidants in human nutrition. Total phenols and anthocyanin content, composition and stability in berry extracts of blackcurrant interspecific hybrids, and antioxidative activity of extracts was evaluated. Berries of interspecific hybrids accumulated 530 to 614 mg 100 g(-1) FW of total phenolic compounds, while 621 mg 100 g(-1) FW of phenolics was established in berries of control Ribes nigrum cultivar 'Ben Tirran'. 'Ben Tirran' berries accumulated 444 mg 100 g(-1) FW of anthocyanins and higher amount was identified in berries of interspecific hybrids No. 11-13 (R. nigrum × R. petraeum) and No. 57 (R. nigrum × R. aureum), 522 and 498 mg100 g(-1) FW respectively. Berry extracts of hybrid No. 11-13 distinguished by the highest antioxidative activity (80%) and it was higher than antioxidant activity of 'Ben Tirran' (70%). Antioxidative activity of all tested berry extracts (70-80%) was twice higher compared to synthetic antioxidant BHT (39%). However correlation between phenolics or total anthocyanin content and antioxidative activity degree was not established. Amount of cyanidin 3-O-glucoside and cyanidin 3-O-rutinoside in berries of hybrids No. 57, No. 11-13 and No. 8 ((R. nigrum × R. americanum) × (R. nigrum × R. americanum)) was higher than in berries of 'Ben Tirran'. It was established that cyanidins are more stable anthocyanins in all studied temperature and irradiation conditions. Therefore interspecific hybrids No. 57 and No. 11-13 were the most agronomically valuable hybrids.

Phenolics, antioxidative activity and characterization of anthocyanins in berries of blackcurrant interspecific hybrids

The interest in phenols and anthocyanins has increased due to their antioxidant properties and to their potential usage as dietary antioxidants in human nutrition. Total phenols and anthocyanin content, composition and stability in berry extracts of blackcurrant interspecific hybrids, and antioxidative activity of extracts was evaluated. Berries of interspecific hybrids accumulated 530 to 614 mg 100 g(-1) FW of total phenolic compounds, while 621 mg 100 g(-1) FW of phenolics was established in berries of control Ribes nigrum cultivar 'Ben Tirran'. 'Ben Tirran' berries accumulated 444 mg 100 g(-1) FW of anthocyanins and higher amount was identified in berries of interspecific hybrids No. 11-13 (R. nigrum × R. petraeum) and No. 57 (R. nigrum × R. aureum), 522 and 498 mg100 g(-1) FW respectively. Berry extracts of hybrid No. 11-13 distinguished by the highest antioxidative activity (80%) and it was higher than antioxidant activity of 'Ben Tirran' (70%). Antioxidative activity of all tested berry extracts (70-80%) was twice higher compared to synthetic antioxidant BHT (39%). However correlation between phenolics or total anthocyanin content and antioxidative activity degree was not established. Amount of cyanidin 3-O-glucoside and cyanidin 3-O-rutinoside in berries of hybrids No. 57, No. 11-13 and No. 8 ((R. nigrum × R. americanum) × (R. nigrum × R. americanum)) was higher than in berries of 'Ben Tirran'. It was established that cyanidins are more stable anthocyanins in all studied temperature and irradiation conditions. Therefore interspecific hybrids No. 57 and No. 11-13 were the most agronomically valuable hybrids.