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

Abstract

Horticultural crops of the <i>Ribes</i> 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 <i>Ribes</i> genus. Transcription levels of anthocyanin synthesis enzymes and the regulatory gene <i>RrMYB10</i> correlated with fruit coloration and anthocyanin quantities of different <i>Ribes</i> cultivars. Regulatory genes were tested for the ability to modulate anthocyanin biosynthesis during transient expression in the leaves of two <i>Nicotiana</i> species and to activate <i>Prunus avium</i> promoters of late anthocyanin biosynthesis genes in <i>N. tabacum</i>. Functional tests showed a strong capability of <i>RrMyb10</i> to induce anthocyanin synthesis in a heterologous system, even without the concurrent expression of any heterologous bHLH, whereas <i>RrbHLH3</i> enhanced MYB-induced anthocyanin synthesis. Data obtained in this work facilitate further analysis of the anthocyanin synthesis pathway in key <i>Ribes</i> species, and potent anthocyanin inducer <i>RrMyb10</i> can be used to manipulate anthocyanin expression in heterologous systems.