title: Cryptochrome 2 and phototropin 2 regulate resistance protein-mediated viral defense by negatively regulating an E3 ubiquitin ligase.
abstract: Light harvested by plants is essential for the survival of most life forms. This light perception ability requires the activities of proteins termed photoreceptors. We report a function for photoreceptors in mediating resistance (R) protein-derived plant defense. The blue-light photoreceptors, cryptochrome (CRY) 2 and phototropin (PHOT) 2, are required for the stability of the R protein HRT, and thereby resistance to Turnip Crinkle virus (TCV). Exposure to darkness or blue-light induces degradation of CRY2, and in turn HRT, resulting in susceptibility. Overexpression of HRT can compensate for the absence of PHOT2 but not CRY2. HRT does not directly associate with either CRY2 or PHOT2 but does bind the CRY2-/PHOT2-interacting E3 ubiquitin ligase, COP1. Application of the proteasome inhibitor, MG132, prevents blue-light-dependent degradation of HRT, consequently these plants show resistance to TCV under blue-light. We propose that CRY2/PHOT2 negatively regulate the proteasome-mediated degradation of HRT, likely via COP1, and blue-light relieves this repression resulting in HRT degradation.
authors.affiliation: Department of Plant Pathology, University of Kentucky, Lexington, KY 40546, USA.
authors.forename: Rae-Dong
authors.initials: RD
authors.lastname: Jeong
authors.forename: A C
authors.initials: AC
authors.lastname: Chandra-Shekara
authors.forename: Subhankar Roy
authors.initials: SR
authors.lastname: Barman
authors.forename: Duroy
authors.initials: D
authors.lastname: Navarre
authors.forename: Daniel F
authors.initials: DF
authors.lastname: Klessig
authors.forename: Aardra
authors.initials: A
authors.lastname: Kachroo
authors.forename: Pradeep
authors.initials: P
authors.lastname: Kachroo
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism / Q000821:virology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D019184:Carmovirus / Q000502:physiology; D056931:Cryptochromes / Q000235:genetics / Q000378:metabolism*; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D054884:Host-Pathogen Interactions; D007113:Immunity, Innate / Q000528:radiation effects; D015151:Immunoblotting; D008027:Light; D018613:Microscopy, Confocal; D009154:Mutation; D010935:Plant Diseases / Q000235:genetics / Q000821:virology; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism / Q000821:virology; D030821:Plants, Genetically Modified; D011485:Protein Binding; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D020156:Salicylic Acid / Q000378:metabolism; D015398:Signal Transduction; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; C103618:CRY2 protein, Arabidopsis; D056931:Cryptochromes; C491954:HRT protein, Arabidopsis; C423903:PHOT2 protein, Arabidopsis; D012097:Repressor Proteins; D049452:Green Fluorescent Proteins; C471983:AT2G32950 protein, Arabidopsis; D044767:Ubiquitin-Protein Ligases; D020156:Salicylic Acid