title: TaMYB4 cloned from wheat regulates lignin biosynthesis through negatively controlling the transcripts of both cinnamyl alcohol dehydrogenase and cinnamoyl-CoA reductase genes.
abstract: The subgroup 4 of R2R3-MYB transcription factors has been proposed as repressors regulating the phenylpropanoid pathway. Here, we report a cDNA encoding a subgroup 4 R2R3-MYB factor from wheat, designated as TaMYB4. A phylogenetic analysis showed that TaMYB4 is in a subclade that is specific to monocot plants. The TaMYB4 gene was highly expressed in stem and root tissues. In vitro binding analysis in yeast cells showed TaMYB4 interacted with OsCAD2 promoter characterized by an AC-II element that has been considered as the MYB-binding site in lignin biosynthetic genes. The overexpression of TaMYB4 in transgenic tobacco led to transcriptional reduction of both cinnamyl alcohol dehydrogenase (CAD) and cinnamoyl-CoA reductase (CCR) genes involved in the lignin biosynthesis. Enzymatic assay showed reduction of CAD and CCR activities in the transgenic tobacco plants that substantially decreased the levels of total lignin but increased it's ratio of S/G. In addition, the total flavonoid content was increased in transgenic tobacco leaves, suggesting that the overexpression of TaMYB4 likely led to a redirection of the metabolic flux from the lignin pathway to the flavonoid pathway. These data suggest that TaMYB4 negatively regulates the lignin biosynthesis in wheat.
authors.affiliation: Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, 20 Nanxin Cun, Xiangshan, Beijing, China. mqh@ibcas.ac.cn
authors.forename: Qing-Hu
authors.initials: QH
authors.lastname: Ma
authors.forename: Cui
authors.initials: C
authors.lastname: Wang
authors.forename: Hai-Hao
authors.initials: HH
authors.lastname: Zhu
mesh_terms: D000429:Alcohol Oxidoreductases / Q000235:genetics* / Q000378:metabolism; D000445:Aldehyde Oxidoreductases / Q000235:genetics* / Q000378:metabolism; D003001:Cloning, Molecular; D005419:Flavonoids / Q000378:metabolism; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D008031:Lignin / Q000096:biosynthesis*; D008969:Molecular Sequence Data; D010802:Phylogeny; D018515:Plant Leaves / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D030821:Plants, Genetically Modified; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014026:Nicotiana / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D014908:Triticum / Q000235:genetics*
chemical_list: D005419:Flavonoids; D010940:Plant Proteins; D008031:Lignin; D000429:Alcohol Oxidoreductases; C018656:cinnamyl alcohol dehydrogenase; D000445:Aldehyde Oxidoreductases; C019904:cinnamoyl CoA reductase