title: Arabidopsis HSP90 protein modulates RPP4-mediated temperature-dependent cell death and defense responses.
abstract: Plant defense responses are regulated by temperature. In Arabidopsis, the chilling-sensitive mutant chs2-1 (rpp4-1d) contains a gain-of-function mutation in the TIR-NB-LRR (Toll and interleukin 1 receptor-nucleotide binding-leucine-rich repeat) gene, RPP4 (RECOGNITION OF PERONOSPORA PARASITICA 4), which leads to constitutive activation of the defense response at low temperatures. Here, we identified and characterized two suppressors of rpp4-1d from a genetic screen, hsp90.2 and hsp90.3, which carry point mutations in the cytosolic heat shock proteins HSP90.2 and HSP90.3, respectively. The hsp90 mutants suppressed the chilling sensitivity of rpp4-1d, including seedling lethality, activation of the defense responses and cell death under chilling stress. The hsp90 mutants exhibited compromised RPM1 (RESISTANCE TO PSEUDOMONAS MACULICOLA 1)-, RPS4 (RESISTANCE TO P. SYRINGAE 4)- and RPP4-mediated pathogen resistance. The wild-type RPP4 and the mutated form rpp4 could interact with HSP90 to form a protein complex. Furthermore, RPP4 and rpp4 proteins accumulated in the cytoplasm and nucleus at normal temperatures, whereas the nuclear accumulation of the mutated rpp4 was decreased at low temperatures. Genetic analysis of the intragenic suppressors of rpp4-1d revealed the important functions of the NB-ARC and LRR domains of RPP4 in temperature-dependent defense signaling. In addition, the rpp4-1d-induced chilling sensitivity was largely independent of the WRKY70 or MOS (modifier of snc1) genes. [Correction added after online publication 11 March 2013: the expansions of TIR-NB-LRR and RPS4 were amended] This study reveals that Arabidopsis HSP90 regulates RPP4-mediated temperature-dependent cell death and defense responses.
authors.affiliation: State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, National Plant Gene Research Center, China Agricultural University, Beijing, 100193, China.
authors.forename: Fei
authors.initials: F
authors.lastname: Bao
authors.affiliation: State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, National Plant Gene Research Center, China Agricultural University, Beijing, 100193, China.
authors.forename: Xiaozhen
authors.initials: X
authors.lastname: Huang
authors.affiliation: Michael Smith Laboratories, University of British Columbia, Vancouver, Canada.
authors.forename: Chipan
authors.initials: C
authors.lastname: Zhu
authors.affiliation: State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, National Plant Gene Research Center, China Agricultural University, Beijing, 100193, China.
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Michael Smith Laboratories, University of British Columbia, Vancouver, Canada.
authors.forename: Xin
authors.initials: X
authors.lastname: Li
authors.affiliation: State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, National Plant Gene Research Center, China Agricultural University, Beijing, 100193, China.
authors.forename: Shuhua
authors.initials: S
authors.lastname: Yang
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000235:genetics* / Q000276:immunology / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D016923:Cell Death; D018506:Gene Expression Regulation, Plant; D018841:HSP90 Heat-Shock Proteins / Q000235:genetics* / Q000378:metabolism; D008954:Models, Biological; D010641:Phenotype; D010935:Plant Diseases / Q000276:immunology; D057865:Plant Immunity; D017354:Point Mutation; D020033:Protein Isoforms; D036226:Seedlings / Q000166:cytology / Q000235:genetics / Q000276:immunology / Q000502:physiology; D013696:Temperature
chemical_list: D029681:Arabidopsis Proteins; D018841:HSP90 Heat-Shock Proteins; C543879:Hsp90-2 protein, Arabidopsis; C500134:Hsp90-3 protein, Arabidopsis; D020033:Protein Isoforms; C107295:RPP5 protein, Arabidopsis
keywords: Arabidopsis; HSP90 proteins; RPP4; cell death; low temperature