title: UV-B Perceived by the UVR8 Photoreceptor Inhibits Plant Thermomorphogenesis.
abstract: Small increases in ambient temperature can elicit striking effects on plant architecture, collectively termed thermomorphogenesis [1]. In Arabidopsis thaliana, these include marked stem elongation and leaf elevation, responses that have been predicted to enhance leaf cooling [2-5]. Thermomorphogenesis requires increased auxin biosynthesis, mediated by the bHLH transcription factor PHYTOCHROME-INTERACTING FACTOR 4 (PIF4) [6-8], and enhanced stability of the auxin co-receptor TIR1, involving HEAT SHOCK PROTEIN 90 (HSP90) [9]. High-temperature-mediated hypocotyl elongation additionally involves localized changes in auxin metabolism, mediated by the indole-3-acetic acid (IAA)-amido synthetase Gretchen Hagen 3 (GH3).17 [10]. Here we show that ultraviolet-B light (UV-B) perceived by the photoreceptor UV RESISTANCE LOCUS 8 (UVR8) [11] strongly attenuates thermomorphogenesis via multiple mechanisms inhibiting PIF4 activity. Suppression of thermomorphogenesis involves UVR8 and CONSTITUTIVELY PHOTOMORPHOGENIC 1 (COP1)-mediated repression of PIF4 transcript accumulation, reducing PIF4 abundance. UV-B also stabilizes the bHLH protein LONG HYPOCOTYL IN FAR RED (HFR1), which can bind to and inhibit PIF4 function. Collectively, our results demonstrate complex crosstalk between UV-B and high-temperature signaling. As plants grown in sunlight would most likely experience concomitant elevations in UV-B and ambient temperature, elucidating how these pathways are integrated is of key importance to the understanding of plant development in natural environments.
authors.affiliation: School of Biological Sciences, Life Sciences Building, University of Bristol, Bristol BS8 1TQ, UK; Plant Ecophysiology, Institute of Environmental Biology (IEB), Utrecht University, Padualaan 8, 3584 Utrecht, the Netherlands.
authors.forename: Scott
authors.initials: S
authors.lastname: Hayes
authors.affiliation: School of Biological Sciences, Life Sciences Building, University of Bristol, Bristol BS8 1TQ, UK.
authors.forename: Ashutosh
authors.initials: A
authors.lastname: Sharma
authors.affiliation: School of Biological Sciences, Life Sciences Building, University of Bristol, Bristol BS8 1TQ, UK.
authors.forename: Donald P
authors.initials: DP
authors.lastname: Fraser
authors.affiliation: Centre for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, 1015 Lausanne, Switzerland.
authors.forename: Martine
authors.initials: M
authors.lastname: Trevisan
authors.affiliation: School of Biological Sciences, Life Sciences Building, University of Bristol, Bristol BS8 1TQ, UK.
authors.forename: C Kester
authors.initials: CK
authors.lastname: Cragg-Barber
authors.affiliation: Department of Botany and Plant Biology, University of Geneva, Sciences III, 30 Quai E. Ansermet, 1211 Geneva 4, Switzerland.
authors.forename: Eleni
authors.initials: E
authors.lastname: Tavridou
authors.affiliation: Centre for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, 1015 Lausanne, Switzerland.
authors.forename: Christian
authors.initials: C
authors.lastname: Fankhauser
authors.affiliation: Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK.
authors.forename: Gareth I
authors.initials: GI
authors.lastname: Jenkins
authors.affiliation: School of Biological Sciences, Life Sciences Building, University of Bristol, Bristol BS8 1TQ, UK. Electronic address: kerry.franklin@bristol.ac.uk.
authors.forename: Keara A
authors.initials: KA
authors.lastname: Franklin
mesh_terms: D017360:Arabidopsis / Q000254:growth & development* / Q000378:metabolism / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects*; D006358:Hot Temperature; D018547:Plant Stems / Q000254:growth & development* / Q000378:metabolism / Q000528:radiation effects; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism; D014466:Ultraviolet Rays / Q000009:adverse effects*
chemical_list: D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D002868:Chromosomal Proteins, Non-Histone; D044767:Ubiquitin-Protein Ligases; C459466:PIF4 protein, Arabidopsis; C525052:Uvr8 protein, Arabidopsis; C471983:AT2G32950 protein, Arabidopsis
keywords: Arabidopsis; HFR1; PIF4; UV-B; UVR8; auxin; high temperature; hypocotyl