A constitutively monomeric UVR8 photoreceptor confers enhanced UV-B photomorphogenesis

Proc Natl Acad Sci U S A. 2021 Feb 9;118(6):e2017284118. doi: 10.1073/pnas.2017284118.


The plant ultraviolet-B (UV-B) photoreceptor UVR8 plays an important role in UV-B acclimation and survival. UV-B absorption by homodimeric UVR8 induces its monomerization and interaction with the E3 ubiquitin ligase COP1, leading ultimately to gene expression changes. UVR8 is inactivated through redimerization, facilitated by RUP1 and RUP2. Here, we describe a semidominant, hyperactive allele, namely uvr8-17D, that harbors a glycine-101 to serine mutation. UVR8G101S overexpression led to weak constitutive photomorphogenesis and extreme UV-B responsiveness. UVR8G101S was observed to be predominantly monomeric in vivo and, once activated by UV-B, was not efficiently inactivated. Analysis of a UVR8 crystal structure containing the G101S mutation revealed the distortion of a loop region normally involved in stabilization of the UVR8 homodimer. Plants expressing a UVR8 variant combining G101S with the previously described W285A mutation exhibited robust constitutive photomorphogenesis. This work provides further insight into UVR8 activation and inactivation mechanisms and describes a genetic tool for the manipulation of photomorphogenic responses.

Keywords: UV-B; abiotic stress; acclimation; photoreceptor; signal transduction.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / genetics*
  • Arabidopsis / growth & development
  • Arabidopsis / radiation effects
  • Arabidopsis Proteins / genetics*
  • Chromosomal Proteins, Non-Histone / genetics*
  • Gene Expression Regulation, Plant / radiation effects
  • Mutation / genetics
  • Photoreceptors, Plant / genetics*
  • Signal Transduction / radiation effects
  • Ubiquitin-Protein Ligases / genetics*
  • Ultraviolet Rays


  • Arabidopsis Proteins
  • Chromosomal Proteins, Non-Histone
  • Photoreceptors, Plant
  • Uvr8 protein, Arabidopsis
  • AT2G32950 protein, Arabidopsis
  • Ubiquitin-Protein Ligases