title: HLM1, an essential signaling component in the hypersensitive response, is a member of the cyclic nucleotide-gated channel ion channel family.
abstract: The hypersensitive response (HR) in plants is a programmed cell death that is commonly associated with disease resistance. A novel mutation in Arabidopsis, hlm1, which causes aberrant regulation of cell death, manifested by a lesion-mimic phenotype and an altered HR, segregated as a single recessive allele. Broad-spectrum defense mechanisms remained functional or were constitutive in the mutant plants, which also exhibited increased resistance to a virulent strain of Pseudomonas syringae pv tomato. In response to avirulent strains of the same pathogen, the hlm1 mutant showed differential abilities to restrict bacterial growth, depending on the avirulence gene expressed by the pathogen. The HLM1 gene encodes a cyclic nucleotide-gated channel, CNGC4. Preliminary study of the HLM1/CNGC4 gene pro-duct in Xenopus oocytes (inside-out patch-clamp technique) showed that CNGC4 is permeable to both K(+) and Na(+) and is activated by both cGMP and cAMP. HLM1 gene expression is induced in response to pathogen infection and some pathogen-related signals. Thus, HLM1 might constitute a common downstream component of the signaling pathways leading to HR/resistance.
authors.affiliation: Laboratoire de Biologie Moléculaire des Relations Plantes-Microorganismes, Unité Mixte de Recherche Centre National de la Recherche Scientifique/Institut National de la Recherche Agronomique 215, BP 27, 31326 Castanet-Tolosan cedex, France.
authors.forename: Claudine
authors.initials: C
authors.lastname: Balagué
authors.forename: Baiqing
authors.initials: B
authors.lastname: Lin
authors.forename: Carine
authors.initials: C
authors.lastname: Alcon
authors.forename: Guylaine
authors.initials: G
authors.lastname: Flottes
authors.forename: Susanna
authors.initials: S
authors.lastname: Malmström
authors.forename: Claudia
authors.initials: C
authors.lastname: Köhler
authors.forename: Gunther
authors.initials: G
authors.lastname: Neuhaus
authors.forename: Georges
authors.initials: G
authors.lastname: Pelletier
authors.forename: Frédéric
authors.initials: F
authors.lastname: Gaymard
authors.forename: Dominique
authors.initials: D
authors.lastname: Roby
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis / Q000235:genetics; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism / Q000382:microbiology; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D003001:Cloning, Molecular; D000242:Cyclic AMP / Q000494:pharmacology; D006152:Cyclic GMP / Q000494:pharmacology; D054815:Cyclic Nucleotide-Gated Cation Channels; D005260:Female; D018506:Gene Expression Regulation, Plant; D007113:Immunity, Innate / Q000235:genetics; D007473:Ion Channels / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D009865:Oocytes / Q000187:drug effects / Q000502:physiology; D018408:Patch-Clamp Techniques; D010641:Phenotype; D010802:Phylogeny; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology; D011188:Potassium / Q000378:metabolism; D011549:Pseudomonas / Q000254:growth & development*; D015398:Signal Transduction / Q000235:genetics; D012964:Sodium / Q000378:metabolism; D014981:Xenopus
chemical_list: D029681:Arabidopsis Proteins; D054815:Cyclic Nucleotide-Gated Cation Channels; D007473:Ion Channels; D012964:Sodium; D000242:Cyclic AMP; D006152:Cyclic GMP; D011188:Potassium