title: A lesion-mimic syntaxin double mutant in Arabidopsis reveals novel complexity of pathogen defense signaling.
abstract: The lesion-mimic Arabidopsis mutant, syp121 syp122, constitutively expresses the salicylic acid (SA) signaling pathway and has low penetration resistance to powdery mildew fungi. Genetic analyses of the lesion-mimic phenotype have expanded our understanding of programmed cell death (PCD) in plants. Inactivation of SA signaling genes in syp121 syp122 only partially rescues the lesion-mimic phenotype, indicating that additional defenses contribute to the PCD. Whole genome transcriptome analysis confirmed that SA-induced transcripts, as well as numerous other known pathogen-response transcripts, are up-regulated after inactivation of the syntaxin genes. A suppressor mutant analysis of syp121 syp122 revealed that FMO1, ALD1, and PAD4 are important for lesion development. Mutant alleles of EDS1, NDR1, RAR1, and SGT1b also partially rescued the lesion-mimic phenotype, suggesting that mutating syntaxin genes stimulates TIR-NB-LRR and CC-NB-LRR-type resistances. The syntaxin double knockout potentiated a powdery mildew-induced HR-like response. This required functional PAD4 but not functional SA signaling. However, SA signaling potentiated the PAD4-dependent HR-like response. Analyses of quadruple mutants suggest that EDS5 and SID2 confer separate SA-independent signaling functions, and that FMO1 and ALD1 mediate SA-independent signals that are NPR1-dependent. These studies highlight the contribution of multiple pathways to defense and point to the complexity of their interactions.
authors.affiliation: Plant and Soil Science, Dept of Agricultural Sciences, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark.
authors.forename: Ziguo
authors.initials: Z
authors.lastname: Zhang
authors.forename: Andrea
authors.initials: A
authors.lastname: Lenk
authors.forename: Mats X
authors.initials: MX
authors.lastname: Andersson
authors.forename: Torben
authors.initials: T
authors.lastname: Gjetting
authors.forename: Carsten
authors.initials: C
authors.lastname: Pedersen
authors.forename: Mads E
authors.initials: ME
authors.lastname: Nielsen
authors.forename: Mari-Anne
authors.initials: MA
authors.lastname: Newman
authors.forename: Bi-Huei
authors.initials: BH
authors.lastname: Hou
authors.forename: Shauna C
authors.initials: SC
authors.lastname: Somerville
authors.forename: Hans
authors.initials: H
authors.lastname: Thordal-Christensen
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000502:physiology; D002265:Carboxylic Ester Hydrolases / Q000235:genetics; D002352:Carrier Proteins / Q000502:physiology; D018797:Cell Cycle Proteins / Q000502:physiology; D003517:Cyclopentanes / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000502:physiology; D020869:Gene Expression Profiling; D014644:Genetic Variation / Q000187:drug effects; D047908:Intracellular Signaling Peptides and Proteins; D009154:Mutation; D054883:Oxylipins / Q000494:pharmacology; D010641:Phenotype; D010935:Plant Diseases / Q000235:genetics / Q000517:prevention & control*; D050765:Qa-SNARE Proteins / Q000235:genetics* / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D000637:Transaminases / Q000235:genetics; D014157:Transcription Factors / Q000502:physiology; D014158:Transcription, Genetic
chemical_list: D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D003517:Cyclopentanes; D004268:DNA-Binding Proteins; C118837:EDS1 protein, Arabidopsis; D047908:Intracellular Signaling Peptides and Proteins; C109369:NDR1 protein, Arabidopsis; D054883:Oxylipins; C499581:PBS2 protein, Arabidopsis; C479425:PEN1 protein, Arabidopsis; D050765:Qa-SNARE Proteins; C452192:SGT1b protein, Arabidopsis; D014157:Transcription Factors; C011006:jasmonic acid; C487185:AGD2-LIKE DEFENSE RESPONSE PROTEIN1, Arabidopsis; D000637:Transaminases; D002265:Carboxylic Ester Hydrolases; C400766:PAD4 protein, Arabidopsis