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Dimer/monomer status and in vivo function of salt‐bridge mutants of the plant UV ‐B photoreceptor UVR 8
Author(s) -
Heilmann Monika,
Velanis Christos N.,
Cloix Catherine,
Smith Brian O.,
Christie John M.,
Jenkins Gareth I.
Publication year - 2016
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.13260
Subject(s) - dimer , mutant , arginine , monomer , lysine , salt bridge , in vivo , alanine , asparagine , amino acid , chemistry , biophysics , wild type , biochemistry , stereochemistry , biology , genetics , gene , polymer , organic chemistry
Summary UV RESISTANCE LOCUS 8 ( UVR 8) is a photoreceptor for ultraviolet‐B ( UV ‐B) light that initiates photomorphogenic responses in plants. UV ‐B photoreception causes rapid dissociation of dimeric UVR 8 into monomers that interact with CONSTITUTIVELY PHOTOMORPHOGENIC 1 ( COP 1) to initiate signal transduction. Experiments with purified UVR 8 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 UVR 8 function in plants. Here we evaluate the use of different methods to examine dimer/monomer status of UVR 8 and show that mutations of several salt‐bridge amino acids affect dimer/monomer status, interaction with COP 1 and photoreceptor function of UVR 8 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 COP 1 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 UVR 8 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 UVR 8 has the potential for UV ‐B photoreception, initiating signal transduction and responses in plants.