Nearly all flowering plants produce red/violet anthocyanin pigments. 
Caryophyllales is the only order containing families that replace anthocyanins 
with unrelated red and yellow betalain pigments. Close biological correlation of 
pigmentation patterns suggested that betalains might be regulated by a conserved 
anthocyanin-regulating transcription factor complex consisting of a MYB, a bHLH 
and a WD repeat-containing protein (the MBW complex). Here we show that a 
previously uncharacterized anthocyanin MYB-like protein, Beta vulgaris MYB1 
(BvMYB1), regulates the betalain pathway in beets. Silencing BvMYB1 
downregulates betalain biosynthetic genes and pigmentation, and overexpressing 
BvMYB1 upregulates them. However, unlike anthocyanin MYBs, BvMYB1 will not 
interact with bHLH members of heterologous anthocyanin MBW complexes because of 
identified nonconserved residues. BvMYB1 resides at the historic beet 
pigment-patterning locus, Y, required for red-fleshed beets. We show that Y and 
y express different levels of BvMYB1 transcripts. The co-option of a 
transcription factor regulating anthocyanin biosynthesis would be an important 
evolutionary event allowing betalains to largely functionally replace 
anthocyanins.