title: Rapid reversion from monomer to dimer regenerates the ultraviolet-B photoreceptor UV RESISTANCE LOCUS8 in intact Arabidopsis plants.
abstract: Arabidopsis (Arabidopsis thaliana) UV RESISTANCE LOCUS8 (UVR8) is a photoreceptor that specifically mediates photomorphogenic responses to ultraviolet (UV)-B in plants. UV-B photoreception induces the conversion of the UVR8 dimer into a monomer that interacts with the CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1) protein to regulate gene expression. However, it is not known how the dimeric photoreceptor is regenerated in plants. Here, we show, by using inhibitors of protein synthesis and degradation via the proteasome, that the UVR8 dimer is not regenerated by rapid de novo synthesis following destruction of the monomer. Rather, regeneration occurs by reversion from the monomer to the dimer. However, regeneration of dimeric UVR8 in darkness following UV-B exposure occurs much more rapidly in vivo than in vitro with illuminated plant extracts or purified UVR8, indicating that rapid regeneration requires intact cells. Rapid dimer regeneration in vivo requires protein synthesis, the presence of a carboxyl-terminal 27-amino acid region of UVR8, and the presence of COP1, which is known to interact with the carboxyl-terminal region. However, none of these factors can account fully for the difference in regeneration kinetics in vivo and in vitro, indicating that additional proteins or processes are involved in UVR8 dimer regeneration in vivo.
authors.affiliation: Institute of Molecular, Cell, and Systems Biology, College of Medical, Veterinary, and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom.
authors.forename: Monika
authors.initials: M
authors.lastname: Heilmann
authors.forename: Gareth I
authors.initials: GI
authors.lastname: Jenkins
mesh_terms: D000217:Acyltransferases / Q000378:metabolism; D017360:Arabidopsis / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism*; D003513:Cycloheximide / Q000494:pharmacology; D003624:Darkness; D055519:Photoreceptors, Plant / Q000378:metabolism*; D059828:Plant Cells / Q000187:drug effects / Q000378:metabolism; D010936:Plant Extracts / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000187:drug effects / Q000378:metabolism; D014176:Protein Biosynthesis; D025941:Protein Interaction Mapping; D055503:Protein Multimerization; D059748:Proteolysis; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism; D014466:Ultraviolet Rays
chemical_list: D029681:Arabidopsis Proteins; D002868:Chromosomal Proteins, Non-Histone; D055519:Photoreceptors, Plant; D010936:Plant Extracts; C525052:Uvr8 protein, Arabidopsis; D003513:Cycloheximide; D000217:Acyltransferases; C491135:AT5G13930 protein, Arabidopsis; C471983:AT2G32950 protein, Arabidopsis; D044767:Ubiquitin-Protein Ligases; D046988:Proteasome Endopeptidase Complex