Constitutively active UVR8 photoreceptor variant in Arabidopsis

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 110; no. 50; pp. 20326 - 20331
• Main Authors: Heijde, Marc, Binkert, Melanie, Yin, Ruohe, Ares-Orpel, Florence, Rizzini, Luca, Van De Slijke, Eveline, Persiau, Geert, Nolf, Jonah, Gevaert, Kris, De Jaeger, Geert, Ulm, Roman
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 10-12-2013; NATIONAL ACADEMY OF SCIENCES; National Acad Sciences
• Subjects: Amino acids; Anthocyanins - metabolism; Arabidopsis - genetics; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Biological Sciences; Cell Cycle Proteins - metabolism; Chromatography, Gel; Chromatography, Liquid; Chromosomal Proteins, Non-Histone - genetics; Electrophoresis, Polyacrylamide Gel; Genetic Engineering; Genotype & phenotype; Hypocotyls; Immunoprecipitation; Monomers; Mutation, Missense - genetics; Phenotype; Phenotypes; Photoreceptors; Photoreceptors, Plant - genetics; Plant cells; Plants; Plants, Genetically Modified; Proteins; Real-Time Polymerase Chain Reaction; Seedlings; Tandem Mass Spectrometry; Transgenic plants; Two-Hybrid System Techniques; Ubiquitin-Protein Ligases - metabolism; Yeasts; signal transduction; ultraviolet-B; abiotic stress
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1314336110

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.