Arabidopsis Transcription Factor MYB12 Is a Flavonol-Specific Regulator of Phenylpropanoid Biosynthesis

• Published in: Plant physiology (Bethesda) Vol. 138; no. 2; pp. 1083 - 1096
• Main Authors: Mehrtens, Frank, Kranz, Harald, Bednarek, Pawel, Weisshaar, Bernd
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Biologists 01.06.2005; American Society of Plant Physiologists
• Subjects: Acyltransferases - genetics; Alleles; amino acid sequences; Arabidopsis - genetics; Arabidopsis - metabolism; Arabidopsis Proteins - genetics; Arabidopsis Proteins - physiology; Arabidopsis thaliana; Base Sequence; biochemical pathways; Biological and medical sciences; Biosynthesis; Cell Biology and Signal Transduction; Cells, Cultured; chalcone isomerase; Chromosome Mapping; Chromosomes, Plant; Corn; flavanone 3-hydroxylase; Flavonoids; flavonol synthase; Flavonols; Flavonols - metabolism; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Plant; Genes; Genes. Genome; Molecular and cellular biology; Molecular genetics; molecular sequence data; naringenin-chalcone synthase; nucleotide sequences; Oxidoreductases - genetics; Phenotype; phenylpropanoids; Phenylpropionates - metabolism; plant biochemistry; Plant cells; plant proteins; Plant Proteins - genetics; Polymerase chain reaction; Seedlings; Seedlings - metabolism; Transcription factors; Transcription Factors - physiology; transcriptional activation; Zea mays; Acyltransferases; Monocotyledones; Zea mays; Transcription; Enzyme; Naringenin 3-dioxygenase; Transferases; Biosynthesis; Synthase; Flavanone derivatives; Arabidopsis thaliana; Isomerases; Gene; Cruciferae; Gramineae; Naringenin-chalcone synthase; Dicotyledones; Protoplast; Angiospermae; Spermatophyta; Oxidoreductases; Mutation; Transcription factor
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.104.058032

Comprehensive functional data on plant R2R3-MYB transcription factors is still scarce compared to the manifold of their occurrence. Here, we identified the Arabidopsis (Arabidopsis thaliana) R2R3-MYB transcription factor MYB12 as a flavonol-specific activator of flavonoid biosynthesis. Transient expression in Arabidopsis protoplasts revealed a high degree of functional similarity between MYB12 and the structurally closely related factor P from maize (Zea mays). Both displayed similar target gene specificity, and both activated target gene promoters only in the presence of a functional MYB recognition element. The genes encoding the flavonoid biosynthesis enzymes chalcone synthase, chalcone flavanone isomerase, flavanone 3-hydroxylase, and flavonol synthase were identified as target genes. Hence, our observations further add to the general notion of a close relationship between structure and function of R2R3-MYB factors. High-performance liquid chromatography analyses of myb12 mutant plants and MYB12 overexpression plants demonstrate a tight linkage between the expression level of functional MYB12 and the flavonol content of young seedlings. Quantitative real time reverse transcription-PCR using these mutant plants showed MYB12 to be a transcriptional regulator of CHALCONE SYNTHASE and FLAVONOL SYNTHASE in planta, the gene products of which are indispensable for the biosynthesis of flavonols.