Repression - the Dark Side of Anthocyanin Regulation?

Anthocyanin pigments provide colour to flowers and fruit, and also accumulate in vegetative tissues in response to environmental stress. Anthocyanin synthesis is tightly regulated at the transcriptional level by R2R3-MYB, bHLH and WD-repeat transcription factors, which activate the anthocyanin biosynthetic genes, resulting in anthocyanin accumulation. However, recent insights into the regulation of anthocyanin synthesis from model species highlight the importance of repressive mechanisms for limiting anthocyanin synthesis. The major classes of repressive transcription factors that act to limit the expression of anthocyanin biosynthetic genes are R3- and R2R3-MYB proteins. The activity of these different types of repressors is discussed in the context of developing horticultural and agricultural plants with novel pigmentation patterns and increased levels of these compounds for human or animal health.