Dimer/monomer status and in vivo function of salt-bridge mutants of the plant UV-B photoreceptor UVR8

Heilmann, M., Velanis, C. N., Cloix, C., Smith, B. O., Christie, J. M. and Jenkins, G. I. (2016) Dimer/monomer status and in vivo function of salt-bridge mutants of the plant UV-B photoreceptor UVR8. Plant Journal, 88(1), pp. 71-81. (doi:10.1111/tpj.13260) (PMID:27385642) (PMCID:PMC5091643)

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Abstract

UV RESISTANCE LOCUS8 (UVR8) is a photoreceptor for ultraviolet-B (UV-B) light that initiates photomorphogenic responses in plants. UV-B photoreception causes rapid dissociation of dimeric UVR8 into monomers that interact with CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1) to initiate signal transduction. Experiments with purified UVR8 show that the dimer is maintained by salt-bridge interactions between specific charged amino acids across the dimer interface. However, little is known about the importance of these charged amino acids in determining dimer/monomer status and UVR8 function in plants. Here we evaluate the use of different methods to examine dimer/monomer status of UVR8 and show that mutations of several salt-bridge amino acids affect dimer/monomer status, interaction with COP1 and photoreceptor function of UVR8 in vivo. In particular, the salt-bridges formed between arginine 286 and aspartates 96 and 107 are key to dimer formation. Mutation of arginine 286 to alanine impairs dimer formation, interaction with COP1 and function in vivo, whereas mutation to lysine gives a weakened dimer that is functional in vivo, indicating the importance of the positive charge of the arginine/lysine residue for dimer formation. Notably, a UVR8 mutant in which aspartates 96 and 107 are conservatively mutated to asparagine is strongly impaired in dimer formation but mediates UV-B responses in vivo with a similar dose-response relationship to wild-type. The UV-B responsiveness of this mutant does not correlate with dimer formation and monomerisation, indicating that monomeric UVR8 has the potential for UV-B photoreception, initiating signal transduction and responses in plants.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Jenkins, Professor Gareth and Cloix, Dr Catherine and Velanis, Mr Christos and Heilmann, Miss Monika and Smith, Dr Brian and Christie, Professor John
Authors: Heilmann, M., Velanis, C. N., Cloix, C., Smith, B. O., Christie, J. M., and Jenkins, G. I.
College/School:College of Medical Veterinary and Life Sciences > Institute of Cancer Sciences
College of Medical Veterinary and Life Sciences > Institute of Molecular Cell and Systems Biology
Journal Name:Plant Journal
Publisher:Wiley
ISSN:0960-7412
ISSN (Online):1365-313X
Published Online:05 July 2016
Copyright Holders:Copyright © 2016 The Authors
First Published:First published in Plant Journal 88(1):71-81
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
582521Plant UV-B photoreceptor signallingGareth JenkinsBiotechnology and Biological Sciences Research Council (BBSRC)BB/J008494/1RI MOLECULAR CELL & SYSTEMS BIOLOGY
608621How does the plant UV-B photoreceptor UVR8 initiate signalling?Gareth JenkinsBiotechnology and Biological Sciences Research Council (BBSRC)BB/K00932X/1RI MOLECULAR CELL & SYSTEMS BIOLOGY