title: SR1, a calmodulin-binding transcription factor, modulates plant defense and ethylene-induced senescence by directly regulating NDR1 and EIN3.
abstract: Plant defense responses are tightly controlled by many positive and negative regulators to cope with attacks from various pathogens. Arabidopsis (Arabidopsis thaliana) ENHANCED DISEASE RESISTANCE2 (EDR2) is a negative regulator of powdery mildew resistance, and edr2 mutants display enhanced resistance to powdery mildew (Golovinomyces cichoracearum). To identify components acting in the EDR2 pathway, we screened for edr2 suppressors and identified a gain-of-function mutation in SIGNAL RESPONSIVE1 (SR1), which encodes a calmodulin-binding transcription activator. The sr1-4D gain-of-function mutation suppresses all edr2-associated phenotypes, including powdery mildew resistance, mildew-induced cell death, and ethylene-induced senescence. The sr1-4D single mutant is more susceptible to a Pseudomonas syringae pv tomato DC3000 virulent strain and to avirulent strains carrying avrRpt2 or avrRPS4 than the wild type. We show that SR1 directly binds to the promoter region of NON-RACE-SPECIFIC DISEASE RESISTANCE1 (NDR1), a key component in RESISTANCE TO PSEUDOMONAS SYRINGAE2-mediated plant immunity. Also, the ndr1 mutation suppresses the sr1-1 null allele, which shows enhanced resistance to both P. syringae pv tomato DC3000 avrRpt2 and G. cichoracearum. In addition, we show that SR1 regulates ethylene-induced senescence by directly binding to the ETHYLENE INSENSITIVE3 (EIN3) promoter region in vivo. Enhanced ethylene-induced senescence in sr1-1 is suppressed by ein3. Our data indicate that SR1 plays an important role in plant immunity and ethylene signaling by directly regulating NDR1 and EIN3.
authors.affiliation: State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Haozhen
authors.initials: H
authors.lastname: Nie
authors.forename: Chunzhao
authors.initials: C
authors.lastname: Zhao
authors.forename: Guangheng
authors.initials: G
authors.lastname: Wu
authors.forename: Yingying
authors.initials: Y
authors.lastname: Wu
authors.forename: Yongfang
authors.initials: Y
authors.lastname: Chen
authors.forename: Dingzhong
authors.initials: D
authors.lastname: Tang
mesh_terms: D000595:Amino Acid Sequence; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D017360:Arabidopsis / Q000187:drug effects / Q000254:growth & development* / Q000276:immunology*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001203:Ascomycota / Q000187:drug effects / Q000502:physiology; D001483:Base Sequence; D002118:Calcium / Q000378:metabolism; D002147:Calmodulin / Q000378:metabolism*; D004268:DNA-Binding Proteins; D060467:Disease Resistance / Q000235:genetics / Q000276:immunology; D005030:Ethylenes / Q000494:pharmacology*; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010935:Plant Diseases / Q000276:immunology / Q000382:microbiology; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects; D044224:Pseudomonas syringae / Q000187:drug effects / Q000502:physiology; D013489:Suppression, Genetic / Q000235:genetics; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: C572689:AT2G22300 protein, Arabidopsis; D051017:Apoptosis Regulatory Proteins; D029681:Arabidopsis Proteins; D002147:Calmodulin; D004268:DNA-Binding Proteins; C560397:EDR2 protein, Arabidopsis; C106987:EIN3 protein, Arabidopsis; D005030:Ethylenes; C109369:NDR1 protein, Arabidopsis; D009687:Nuclear Proteins; D014157:Transcription Factors; C036216:ethylene; D002118:Calcium