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      Regulation of the anthocyanin biosynthetic pathway by the TTG1/bHLH/Myb transcriptional complex in Arabidopsis seedlings.

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          Abstract

          In all higher plants studied to date, the anthocyanin pigment pathway is regulated by a suite of transcription factors that include Myb, bHLH and WD-repeat proteins. However, in Arabidopsis thaliana, the Myb regulators remain to be conclusively identified, and little is known about anthocyanin pathway regulation by TTG1-dependent transcriptional complexes. Previous overexpression of the PAP1 Myb suggested that genes from the entire phenylpropanoid pathway are targets of regulation by Myb/bHLH/WD-repeat complexes in Arabidopsis, in contrast to other plants. Here we demonstrate that overexpression of Myb113 or Myb114 results in substantial increases in pigment production similar to those previously seen as a result of over-expression of PAP1, and pigment production in these overexpressors remains TTG1- and bHLH-dependent. Also, plants harboring an RNAi construct targeting PAP1 and three Myb candidates (PAP2, Myb113 and Myb114) showed downregulated Myb gene expression and obvious anthocyanin deficiencies. Correlated with these anthocyanin deficiencies is downregulation of the same late anthocyanin structural genes that are downregulated in ttg1 and bHLH anthocyanin mutants. Expression studies using GL3:GR and TTG1:GR fusions revealed direct regulation of the late biosynthetic genes only. Functional diversification between GL3 and EGL3 with regard to activation of gene targets was revealed by GL3:GR studies in single and double bHLH mutant seedlings. Expression profiles for Myb and bHLH regulators are also presented in the context of pigment production in young seedlings.

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          Author and article information

          Journal
          Plant J
          The Plant journal : for cell and molecular biology
          Wiley
          1365-313X
          0960-7412
          Mar 2008
          : 53
          : 5
          Affiliations
          [1 ] Molecular Cell and Developmental Biology, and Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, TX 78 712, USA. tga@mail.utexas.edu
          Article
          TPJ3373
          10.1111/j.1365-313X.2007.03373.x
          18036197
          ab35e4d0-67c6-4849-9583-714f31c4a3a9
          History

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