Transcriptional control of flavonoid biosynthesis by MYB–bHLH–WDR complexes

• Flavonoid gene expression is tightly regulated by environmental and developmental signals.
• Specific R2R3-MYB and bHLH transcription factors interact with WDR proteins to form MBW complexes.
• MBW complexes contribute to the tight regulation of late biosynthetic gene expression.
• MBW networks provide a powerful model system for the regulation of gene expression.

Flavonoids are widely known for the colors they confer to plant tissues, their contribution to plant fitness and health benefits, and impact on food quality. As convenient biological markers, flavonoids have been instrumental in major genetic and epigenetic discoveries. We review recent advances in the characterization of the underlying regulatory mechanisms of flavonoid biosynthesis, with a special focus on the MBW (MYB–bHLH–WDR) protein complexes. These proteins are well conserved in higher plants. They participate in different types of controls ranging from fine-tuned transcriptional regulation by environmental factors to the initiation of the flavonoid biosynthesis pathway by positive regulatory feedback. The MBW protein complexes provide interesting models for investigating developmentally or environmentally controlled transcriptional regulatory networks.