Ectopic expression of a c1-I allele from maize inhibits pigment formation in the flower of transgenic tobacco.

MYB-related proteins play a key role in regulating the biosynthesis of anthocyanins in plants at the transcriptional level. An MYB gene designated c1-I-2K1 (GenBank accession no. AY237128) was cloned from maize line "2K1 purple," and except for a deletion of nine nucleotides encoding three amino acids right at the carboxyl terminal end of the encoded protein, it was identical to the previously characterized c1-I gene. Flowers of transgenic tobacco overexpressing this c1-I allele showed severe reduction in pigmentation, whereas the pigmentation patterns of flowers of tobacco transformed with both c1-I-2K1 and R homologue gene r-2K1 showed no obvious change. Thus, this c1-I allele appears to act as a repressor in pigment formation and function through titration of a bHLH factor.