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In Arabidopsis thaliana, several MYB and basic helix‐loop‐helix (BHLH) proteins form ternary complexes with TTG1 (WD‐Repeats) and regulate the transcription of genes involved in anthocyanin and proanthocyanidin (PA) biosynthesis. Similar MYB‐BHLH‐WDR (MBW) complexes control epidermal patterning and cell fates. A family of small MYB proteins (R3‐MYB) has been shown to play an important role in the regulation of epidermal cell fates, acting as inhibitors of the MBW complexes. However, so far none of these small MYB proteins have been demonstrated to regulate flavonoid biosynthesis. The genetic and molecular analyses presented here demonstrated that Arabidopsis MYBL2, which encodes a R3‐MYB‐related protein, is involved in the regulation of flavonoid biosynthesis. The loss of MYBL2 activity in the seedlings of two independent T‐DNA insertion mutants led to a dramatic increase in the …