Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/10/2009
Publication Date: 4/10/2009
Citation: Chiu, L., Burke, S., Li, L. 2009. Transcriptional activation of a MYB gene controls the tissue-specific anthocyanin accumulation in a purple cauliflower mutant [abstract]. Plant Biology 2009 Meeting. Interpretive Summary:
Technical Abstract: Flavonoids such as anthocyanins possess significant health benefits to humans and play important physiological roles in plants. An interesting Purple gene mutation in cauliflower confers an abnormal pattern of anthocyanin accumulation, giving intense purple color in very young leaves, curds, and seeds. Through high-resolution genetic mapping, we have isolated the Purple gene and found that it encodes a R2R3-MYB transcription factor that shows tissue-specific expression, consistent with anthocyanin accumulation pattern in the mutant. The Purple gene is tightly linked with other two MYB transcription factors of similar function. Comparison of the DNA sequences between the WT and mutant alleles revealed that the mutation is caused by a unique sequence in the promoter region of the Purple allele. Analysis of Arabidopsis transformants with different fragments of cauliflower promoter-GUS constructs demonstrated that the unique part contains promoter enhancer sequence, causing enhanced expression of the Purple gene. The resulting overexpresson of the Purple gene may activate the expression of a bHLH transcription factor, which together upregulate a subset of anthocyanin structural genes to produce the striking mutant phenotype. Yeast two-hybrid assays showed that the Purple gene encoded MYB protein exhibits stronger interaction with bHLH than other MYBs. Moreover, expression of the Purple allele in transgenic Arabidopsis also results in the tissue-specific accumulation of anthocyanins. These results strongly suggest that the change of genomic context in the promoter of the Purple allele is the genetic basis for the purple cauliflower mutant and the increased expression in Purple transcript levels accounts for the ectopic accumulation of anthocyanins in the mutant plant.