Ultraviolet (UV) radiation is an important constituent of sunlight that determines plant morphology and growth. It induces photomorphogenic responses but also causes damage to DNA. Arabidopsis mutants of the endonucleases that function in nucleotide excision repair, xpf-3 and uvr1-1, showed hypersensitivity to UV-B (280-320nm) in terms of inhibition of hypocotyl growth. SOG1 is a transcription factor that functions in the DNA damage signalling response after γ-irradiation. xpf mutants that carry the sog1-1 mutation showed hypocotyl growth inhibition after UV-B irradiation similar to the wild type. A DNA replication inhibitor, hydroxyurea (HU), also inhibited hypocotyl growth in etiolated seedlings, but xpf-3 was not hypersensitive to HU. UV-B irradiation induced accumulation of the G2/M-specific cell cycle reporter construct CYCB1;1-GUS in wild-type Arabidopsis seedlings that was consistent with the expected accumulation of photodimers and coincided with the time course of hypocotyl growth inhibition after UV-B treatment. Etiolated mutants of UVR8, a recently described UV-B photoreceptor gene, irradiated with UV-B showed inhibition of hypocotyl growth that was not different from that of the wild type, but they lacked UV-B-specific expression of chalcone synthase (CHS), as expected from previous reports. CHS expression after UV-B irradiation was not different in xpf-3 compared with the wild type, nor was it altered after HU treatment. These results suggest that hypocotyl growth inhibition by UV-B light in etiolated Arabidopsis seedlings, a photomorphogenic response, is dictated by signals originating from UV-B absorption by DNA that lead to cell cycle arrest. This process occurs distinct from UVR8 and its signalling pathway responsible for CHS induction.
Bibliographical noteFunding Information:
The authors would like to thank Dr Anne Britt (UC-Davis, CA, USA) for providing the xpf-3, sog1-1, xpf sog1-1 mutants and Col-CYCB1;1:GUS seed, Dr Roman Ulm (University of Geneva, CH) for providing the uvr8-6 mutant, and Dr Gareth Jenkins (University of Glasgow, UK) for providing uvr8-2 seed; the Minnesota Agricultural Experiment Station, the University of Minnesota Graduate School, and the Plant Biological Sciences Graduate Program for financial support; Dr Jerry Cohen and Dr David Kirkpatrick (University of Minnesota, USA) for helpful discussions; and Dr Stefanie Dukowic-Schulze for assistance with GUS staining techniques.
Copyright 2014 Elsevier B.V., All rights reserved.
- DNA repair
- cell cycle arrest
- hypocotyl growth
- nucleotide excision repair