The Arabidopsis bZIP transcription factor HY5 regulates expression of the PFG1/MYB12 gene in response to light and ultraviolet-B radiation

Authors

  • RALF STRACKE,

    1. Department of Biology, Chair of Genome Research, Bielefeld University, D-33594 Bielefeld, Germany,
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      These authors contributed equally to this work.

  • JEAN-JACQUES FAVORY,

    1. Faculty of Biology, Institute of Biology II, University of Freiburg, D-79104 Freiburg, Germany and
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      These authors contributed equally to this work.

  • HENRIETTE GRUBER,

    1. Faculty of Biology, Institute of Biology II, University of Freiburg, D-79104 Freiburg, Germany and
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      These authors contributed equally to this work.

  • LUTZ BARTELNIEWOEHNER,

    1. Department of Biology, Chair of Genome Research, Bielefeld University, D-33594 Bielefeld, Germany,
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  • SEBASTIAN BARTELS,

    1. Faculty of Biology, Institute of Biology II, University of Freiburg, D-79104 Freiburg, Germany and
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  • MELANIE BINKERT,

    1. Faculty of Biology, Institute of Biology II, University of Freiburg, D-79104 Freiburg, Germany and
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  • MARKUS FUNK,

    1. Faculty of Biology, Institute of Biology II, University of Freiburg, D-79104 Freiburg, Germany and
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  • BERND WEISSHAAR,

    1. Department of Biology, Chair of Genome Research, Bielefeld University, D-33594 Bielefeld, Germany,
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  • ROMAN ULM

    Corresponding author
    1. Faculty of Biology, Institute of Biology II, University of Freiburg, D-79104 Freiburg, Germany and
    2. Centre for Biological Signalling Studies (bioss), University of Freiburg, D-79104 Freiburg, Germany
      R. Ulm. Fax: +49 761 2032612; e-mail: roman.ulm@biologie.uni-freiburg.de
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R. Ulm. Fax: +49 761 2032612; e-mail: roman.ulm@biologie.uni-freiburg.de

ABSTRACT

Plants fend off potentially damaging ultraviolet (UV)-B radiation by synthesizing and accumulating UV-B-absorbing flavonols that function as sunscreens. Regulation of this biosynthetic pathway is largely transcriptional and controlled by a network of transcription factors, among which the PRODUCTION OF FLAVONOL GLYCOSIDES (PFG) family of R2R3-MYB transcription factors was recently identified with a pivotal function. Here, we describe the response of Arabidopsis seedlings to narrow-band UV-B radiation at the level of phenylpropanoid pathway genes using whole-genome transcriptional profiling and identify the corresponding flavonol glycosides accumulating under UV-B. We further show that the bZIP transcriptional regulator ELONGATED HYPOCOTYL5 (HY5) is required for the transcriptional activation of the PFG1/MYB12 and PFG3/MYB111 genes under UV-B and visible light. A synthetic protein composed of HY5 with the VP16 activation domain is sufficient to activate PFG1/MYB12 expression in planta. However, even though myb11 myb12 myb111 triple mutants have strongly reduced CHS levels in darkness as well as in constant light, neither light- nor UV-B-inducibility seems impaired. Notwithstanding this, absence of the three PFG family transcription factors results in reduced UV-B tolerance, whereas PFG1/MYB12 overexpression leads to an increased tolerance. Thus, our data suggest that HY5-dependent regulation of PFG gene expression contributes to the establishment of UV-B tolerance.

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