title: The Arabidopsis bZIP transcription factor HY5 regulates expression of the PFG1/MYB12 gene in response to light and ultraviolet-B radiation.
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.
authors.affiliation: Department of Biology, Chair of Genome Research, Bielefeld University, Bielefeld, Germany.
authors.forename: Ralf
authors.initials: R
authors.lastname: Stracke
authors.forename: Jean-Jacques
authors.initials: JJ
authors.lastname: Favory
authors.forename: Henriette
authors.initials: H
authors.lastname: Gruber
authors.forename: Lutz
authors.initials: L
authors.lastname: Bartelniewoehner
authors.forename: Sebastian
authors.initials: S
authors.lastname: Bartels
authors.forename: Melanie
authors.initials: M
authors.lastname: Binkert
authors.forename: Markus
authors.initials: M
authors.lastname: Funk
authors.forename: Bernd
authors.initials: B
authors.lastname: Weisshaar
authors.forename: Roman
authors.initials: R
authors.lastname: Ulm
mesh_terms: D000217:Acyltransferases / Q000378:metabolism; D000872:Anthocyanins / Q000032:analysis; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D050976:Basic-Leucine Zipper Transcription Factors / Q000235:genetics / Q000378:metabolism*; D002734:Chlorophyll / Q000032:analysis; D003001:Cloning, Molecular; D005419:Flavonoids / Q000032:analysis; D018506:Gene Expression Regulation, Plant; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D018749:RNA, Plant / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation; D014466:Ultraviolet Rays
chemical_list: D000872:Anthocyanins; D029681:Arabidopsis Proteins; D050976:Basic-Leucine Zipper Transcription Factors; D005419:Flavonoids; C109254:HY5 protein, Arabidopsis; C504539:MYB12 protein, Arabidopsis; D009687:Nuclear Proteins; D018749:RNA, Plant; D014157:Transcription Factors; D002734:Chlorophyll; D000217:Acyltransferases; C491135:AT5G13930 protein, Arabidopsis