title: Negative regulation of defense responses in Arabidopsis by two NPR1 paralogs.
abstract: NPR1 is required for systemic acquired resistance, and there are five NPR1 paralogs in Arabidopsis. Here we report knockout analysis of two of these, NPR3 and NPR4. npr3 single mutants have elevated basal PR-1 expression and the npr3 npr4 double mutant shows even higher expression. The double mutant plants also display enhanced resistance against virulent bacterial and oomycete pathogens. This enhanced disease resistance is partially dependent on NPR1, can be in part complemented by either wild-type NPR3 or NPR4, and is not associated with an elevated level of salicylic acid. NPR3 and NPR4 interact with TGA2, TGA3, TGA5 and TGA6 in yeast two-hybrid assays. Using bimolecular fluorescence complementation analysis, we show that NPR3 interacts with TGA2 in the nucleus of onion epidermal cells and Arabidopsis mesophyll protoplasts. Combined with our previous finding that basal PR-1 levels are also elevated in the tga2 tga5 tga6 triple mutant, we propose that NPR3 and NPR4 negatively regulate PR gene expression and pathogen resistance through their association with TGA2 and its paralogs.
authors.affiliation: National Institute of Biological Sciences, #7 Science Park Road, Zhongguancun Life Science Park, Beijing, People's Republic of China 102206. zhangyuelin@nibs.ac.cn
authors.forename: Yuelin
authors.initials: Y
authors.lastname: Zhang
authors.forename: Yu Ti
authors.initials: YT
authors.lastname: Cheng
authors.forename: Na
authors.initials: N
authors.lastname: Qu
authors.forename: Qingguo
authors.initials: Q
authors.lastname: Zhao
authors.forename: Donglin
authors.initials: D
authors.lastname: Bi
authors.forename: Xin
authors.initials: X
authors.lastname: Li
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D018506:Gene Expression Regulation, Plant; D009154:Mutation; D010935:Plant Diseases; D020156:Salicylic Acid / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; C105496:NPR1 protein, Arabidopsis; C517740:NPR3 protein, Arabidopsis; C502134:NPR4 protein, Arabidopsis; D014157:Transcription Factors; D020156:Salicylic Acid