Activation of the maize anthocyanin gene a2 is mediated by an element conserved in many anthocyanin promoters.
Two transcription factors, C1 (a Myb-domain protein) and B (a basic-helix-loop-helix protein), mediate transcriptional activation of the anthocyanin-biosynthetic genes of maize (Zea mays). To begin to assess the mechanism of activation, the sequences required for C1- and B-mediated induction have been determined for the a2 promoter, which encodes an anthocyanin-biosynthetic enzyme. Analysis of a series of 7- to 13-base-pair substitutions revealed two regions crucial for activation. One region, centered at -99, contained a C1-binding site that abolished C1 binding. The other crucial region was adjacent, centered at -91. C1 binding was not detected at this site, and mutation of this site did not prevent C1 binding at -99. An oligonucleotide dimer containing these two crucial elements was sufficient for C1 and B activation of a heterologous promoter. These data suggest that activation of the anthocyanin genes involves C1 and another factor binding at closely adjacent sites. Mutating a previously postulated anthocyanin consensus sequence within a2 did not significantly reduce activation by C1 and B. However, sequence comparisons of the crucial a2 regions with sequences important for C1- and B-mediated activation in two other anthocyanin promoters led to a revised consensus element shared by these promoters.
Lesnick
M L
ML
Institute of Molecular Biology, University of Oregon, Eugene, Oregon 97403, USA.
Chandler
V L
VL
D000872:Anthocyanins / Q000096:biosynthesis* / Q000235:genetics*; D001483:Base Sequence; D003001:Cloning, Molecular; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D016415:Sequence Alignment; D012689:Sequence Homology, Nucleic Acid; D003313:Zea mays / Q000235:genetics* / Q000378:metabolism
D000872:Anthocyanins