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

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

Author information

1
Department of Botany and Plant Biology, University of Geneva, CH-1211 Geneva 4, Switzerland;
2
Department of Botany and Plant Biology, University of Geneva, CH-1211 Geneva 4, Switzerland; Institute of Genetics and Genomics of Geneva, University of Geneva, CH-1211 Geneva 4, Switzerland roman.ulm@unige.ch.

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

PMID:
27407149
PMCID:
PMC4968759
DOI:
10.1073/pnas.1607074113
[Indexed for MEDLINE]
Free PMC Article

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