title: Dysfunction of Arabidopsis MACPF domain protein activates programmed cell death via tryptophan metabolism in MAMP-triggered immunity.
abstract: Plant immune responses triggered upon recognition of microbe-associated molecular patterns (MAMPs) typically restrict pathogen growth without a host cell death response. We isolated two Arabidopsis mutants, derived from accession Col-0, that activated cell death upon inoculation with nonadapted fungal pathogens. Notably, the mutants triggered cell death also when treated with bacterial MAMPs such as flg22. Positional cloning identified NSL1 (Necrotic Spotted Lesion 1) as a responsible gene for the phenotype of the two mutants, whereas nsl1 mutations of the accession No-0 resulted in necrotic lesion formation without pathogen inoculation. NSL1 encodes a protein of unknown function containing a putative membrane-attack complex/perforin (MACPF) domain. The application of flg22 increased salicylic acid (SA) accumulation in the nsl1 plants derived from Col-0, while depletion of isochorismate synthase 1 repressed flg22-inducible lesion formation, indicating that elevated SA is needed for the cell death response. nsl1 plants of Col-0 responded to flg22 treatment with an RBOHD-dependent oxidative burst, but this response was dispensable for the nsl1-dependent cell death. Surprisingly, loss-of-function mutations in PEN2, involved in the metabolism of tryptophan (Trp)-derived indole glucosinolates, suppressed the flg22-induced and nsl1-dependent cell death. Moreover, the increased accumulation of SA in the nsl1 plants was abrogated by blocking Trp-derived secondary metabolite biosynthesis, whereas the nsl1-dependent hyperaccumulation of PEN2-dependent compounds was unaffected when the SA biosynthesis pathway was blocked. Collectively, these findings suggest that MAMP-triggered immunity activates a genetically programmed cell death in the absence of the functional MACPF domain protein NSL1 via Trp-derived secondary metabolite-mediated activation of the SA pathway.
authors.affiliation: Graduate School of Agriculture, Kyoto University, Kyoto, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Fukunaga
authors.affiliation: Graduate School of Agriculture, Kyoto University, Kyoto, Japan.
authors.forename: Miho
authors.initials: M
authors.lastname: Sogame
authors.affiliation: Graduate School of Agriculture, Kyoto University, Kyoto, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Hata
authors.affiliation: Graduate School of Agriculture, Kyoto University, Kyoto, Japan.
authors.forename: Suthitar
authors.initials: S
authors.lastname: Singkaravanit-Ogawa
authors.affiliation: Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland.
authors.forename: Mariola
authors.initials: M
authors.lastname: Piślewska-Bednarek
authors.affiliation: Graduate School of Agriculture, Kyoto University, Kyoto, Japan.
authors.forename: Mariko
authors.initials: M
authors.lastname: Onozawa-Komori
authors.affiliation: Advanced Science Research Center, Kanazawa University, Kanazawa, Japan.
authors.forename: Takumi
authors.initials: T
authors.lastname: Nishiuchi
authors.affiliation: Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Japan.
authors.forename: Kei
authors.initials: K
authors.lastname: Hiruma
authors.affiliation: Iwate Biotechnology Research Center, Iwate, Japan.
authors.forename: Hiromasa
authors.initials: H
authors.lastname: Saitoh
authors.affiliation: Iwate Biotechnology Research Center, Iwate, Japan.
authors.forename: Ryohei
authors.initials: R
authors.lastname: Terauchi
authors.affiliation: Graduate School of Agriculture, Kyoto University, Kyoto, Japan.
authors.forename: Saeko
authors.initials: S
authors.lastname: Kitakura
authors.affiliation: Graduate School of Agriculture, Kyoto University, Kyoto, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Inoue
authors.affiliation: Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland.
authors.forename: Paweł
authors.identifier: 0000-0002-3064-7775
authors.initials: P
authors.lastname: Bednarek
authors.affiliation: Department of Plant-Microbe Interactions, Max Planck Institute for Plant Breeding Research, Cologne, Germany.
authors.forename: Paul
authors.initials: P
authors.lastname: Schulze-Lefert
authors.affiliation: Graduate School of Agriculture, Kyoto University, Kyoto, Japan.
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Takano
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000276:immunology* / Q000382:microbiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D016923:Cell Death / Q000276:immunology; D002462:Cell Membrane / Q000378:metabolism; D020231:Colletotrichum / Q000472:pathogenicity; D018506:Gene Expression Regulation, Plant; D014644:Genetic Variation; D049452:Green Fluorescent Proteins / Q000235:genetics; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D059828:Plant Cells / Q000378:metabolism; D018515:Plant Leaves; D030821:Plants, Genetically Modified; D000072417:Protein Domains; D017382:Reactive Oxygen Species / Q000378:metabolism; D020156:Salicylic Acid / Q000378:metabolism; D014364:Tryptophan / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D049452:Green Fluorescent Proteins; D009687:Nuclear Proteins; D017382:Reactive Oxygen Species; D020156:Salicylic Acid; D014364:Tryptophan; C000624411:NSL1 protein, Arabidopsis
keywords: 
  Colletotrichum orbiculare
  ; MACPF domain; MAMPs; Tryptophan-derived metabolism; cell death; salicylic acid signaling; secondary metabolites