title: The Arabidopsis transcription factor MYB12 is a flavonol-specific regulator of phenylpropanoid biosynthesis.
abstract: 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.
authors.affiliation: Max-Planck-Institute for Plant Breeding Research, D-50829 Cologne, Germany.
authors.forename: Frank
authors.initials: F
authors.lastname: Mehrtens
authors.forename: Harald
authors.initials: H
authors.lastname: Kranz
authors.forename: Pawel
authors.initials: P
authors.lastname: Bednarek
authors.forename: Bernd
authors.initials: B
authors.lastname: Weisshaar
mesh_terms: D000217:Acyltransferases / Q000235:genetics; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000502:physiology*; D001483:Base Sequence; D002478:Cells, Cultured; D002874:Chromosome Mapping; D032461:Chromosomes, Plant; D044948:Flavonols / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D010088:Oxidoreductases / Q000235:genetics; D010641:Phenotype; D010666:Phenylpropionates / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics; D036226:Seedlings / Q000378:metabolism; D014157:Transcription Factors / Q000502:physiology*
chemical_list: D029681:Arabidopsis Proteins; D044948:Flavonols; C504539:MYB12 protein, Arabidopsis; D010666:Phenylpropionates; D010940:Plant Proteins; D014157:Transcription Factors; D010088:Oxidoreductases; C085313:flavonol synthase; D000217:Acyltransferases; C491135:AT5G13930 protein, Arabidopsis