title: Constitutively active UVR8 photoreceptor variant in Arabidopsis.
abstract: Arabidopsis thaliana UV RESISTANCE LOCUS 8 (UVR8) is a UV-B photoreceptor that initiates photomorphogenic responses underlying acclimation and UV-B tolerance in plants. UVR8 is a homodimer in its ground state, and UV-B exposure results in its instantaneous monomerization followed by interaction with CONSTITUTIVELY PHOTOMORPHOGENIC 1 (COP1), a major factor in UV-B signaling. UV-B photoreception by UVR8 is based on intrinsic tryptophan aromatic amino acid residues, with tryptophan-285 as the main chromophore. We generated transgenic plants expressing UVR8 with a single amino acid change of tryptophan-285 to alanine. UVR8(W285A) appears monomeric and shows UV-B-independent interaction with COP1. Phenotypically, the plants expressing UVR8(W285A) exhibit constitutive photomorphogenesis associated with constitutive activation of target genes, elevated levels of anthocyanins, and enhanced, acclimation-independent UV-B tolerance. Moreover, we have identified COP1, REPRESSOR OF UV-B PHOTOMORPHOGENESIS 1 and 2 (RUP1 and RUP2), and the SUPPRESSOR OF PHYA-105 (SPA) family as proteins copurifying with UVR8(W285A). Whereas COP1, RUP1, and RUP2 are known to directly interact with UVR8, we show that SPA1 interacts with UVR8 indirectly through COP1. We conclude that UVR8(W285A) is a constitutively active UVR8 photoreceptor variant in Arabidopsis, as is consistent with the crucial importance of monomer formation and COP1 binding for UVR8 activity.
authors.affiliation: Department of Botany and Plant Biology, Sciences III, University of Geneva, CH-1211 Geneva 4, Switzerland.
authors.forename: Marc
authors.initials: M
authors.lastname: Heijde
authors.forename: Melanie
authors.initials: M
authors.lastname: Binkert
authors.forename: Ruohe
authors.initials: R
authors.lastname: Yin
authors.forename: Florence
authors.initials: F
authors.lastname: Ares-Orpel
authors.forename: Luca
authors.initials: L
authors.lastname: Rizzini
authors.forename: Eveline
authors.initials: E
authors.lastname: Van De Slijke
authors.forename: Geert
authors.initials: G
authors.lastname: Persiau
authors.forename: Jonah
authors.initials: J
authors.lastname: Nolf
authors.forename: Kris
authors.initials: K
authors.lastname: Gevaert
authors.forename: Geert
authors.initials: G
authors.lastname: De Jaeger
authors.forename: Roman
authors.initials: R
authors.lastname: Ulm
mesh_terms: D000872:Anthocyanins / Q000378:metabolism; D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000378:metabolism; D002850:Chromatography, Gel; D002853:Chromatography, Liquid; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics*; D004591:Electrophoresis, Polyacrylamide Gel; D005818:Genetic Engineering; D047468:Immunoprecipitation; D020125:Mutation, Missense / Q000235:genetics; D010641:Phenotype; D055519:Photoreceptors, Plant / Q000235:genetics*; D030821:Plants, Genetically Modified; D060888:Real-Time Polymerase Chain Reaction; D053719:Tandem Mass Spectrometry; D020798:Two-Hybrid System Techniques; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism
chemical_list: D000872:Anthocyanins; D029681:Arabidopsis Proteins; D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D055519:Photoreceptors, Plant; C118571:SPA1 protein, Arabidopsis; C525052:Uvr8 protein, Arabidopsis; C471983:AT2G32950 protein, Arabidopsis; D044767:Ubiquitin-Protein Ligases
keywords: abiotic stress; signal transduction; ultraviolet-B