COP1 is required for UV-B-induced nuclear accumulation of the UVR8 photoreceptor

Proc Natl Acad Sci U S A. 2016 Jul 26;113(30):E4415-22. doi: 10.1073/pnas.1607074113. Epub 2016 Jul 12.

Abstract

The UV-B photoreceptor UV RESISTANCE LOCUS 8 (UVR8) promotes UV-B acclimation and tolerance in Arabidopsis thaliana UVR8 localizes to both cytosol and nucleus, but its main activity is assumed to be nuclear. UV-B photoreception stimulates nuclear accumulation of UVR8 in a presently unknown manner. Here, we show that CONSTITUTIVELY PHOTOMORPHOGENIC 1 (COP1) is required for UV-B-induced nuclear accumulation of UVR8, but bypassing the COP1 requirement for UVR8 nuclear accumulation did not rescue the cop1 mutant UV-B phenotype. Using a glucocorticoid receptor (GR)-based fusion protein system to conditionally localize GR-UVR8 to the nucleus, we have demonstrated that both photoactivation and nuclear localization of UVR8 are required for UV-B-induced photomorphogenic responses. In contrast, there was no UV-B response when UV-B-activated UVR8 was artificially retained in the cytosol. In agreement with a predominantly nuclear activity, constitutively active UVR8(W285A) accumulated in the nucleus also in the absence of UV-B. Furthermore, GR-COP1 expression lines suggested that UV-B-activated UVR8 can be coimported into the nucleus by COP1. Our data strongly support localization of UVR8 signaling in the nucleus and a dual role for COP1 in the regulation of UV-B-induced UVR8 nuclear accumulation and in UVR8-mediated UV-B signaling.

Keywords: COP1; UV-B photoreceptor; UVR8; glucocorticoid receptor; nuclear accumulation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Active Transport, Cell Nucleus / radiation effects
  • Arabidopsis / genetics
  • Arabidopsis / metabolism
  • Arabidopsis / radiation effects
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism*
  • Cell Nucleus / metabolism*
  • Cell Nucleus / radiation effects
  • Chromosomal Proteins, Non-Histone / genetics
  • Chromosomal Proteins, Non-Histone / metabolism
  • Gene Expression Regulation, Plant
  • Immunoblotting
  • Mutation
  • Photoreceptors, Plant / genetics
  • Photoreceptors, Plant / metabolism*
  • Plants, Genetically Modified
  • Signal Transduction / genetics
  • Ubiquitin-Protein Ligases
  • Ultraviolet Rays

Substances

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