title: Nep1-like proteins from three kingdoms of life act as a microbe-associated molecular pattern in Arabidopsis.
abstract: Necrosis and ethylene-inducing peptide 1 (Nep1)-like proteins (NLPs) are secreted by a wide range of plant-associated microorganisms. They are best known for their cytotoxicity in dicot plants that leads to the induction of rapid tissue necrosis and plant immune responses. The biotrophic downy mildew pathogen Hyaloperonospora arabidopsidis encodes 10 different noncytotoxic NLPs (HaNLPs) that do not cause necrosis. We discovered that these noncytotoxic NLPs, however, act as potent activators of the plant immune system in Arabidopsis thaliana. Ectopic expression of HaNLP3 in Arabidopsis triggered resistance to H. arabidopsidis, activated the expression of a large set of defense-related genes, and caused a reduction of plant growth that is typically associated with strongly enhanced immunity. N- and C-terminal deletions of HaNLP3, as well as amino acid substitutions, pinpointed to a small central region of the protein that is required to trigger immunity, indicating the protein acts as a microbe-associated molecular pattern (MAMP). This was confirmed in experiments with a synthetic peptide of 24 aa, derived from the central part of HaNLP3 and corresponding to a conserved region in type 1 NLPs that induces ethylene production, a well-known MAMP response. Strikingly, corresponding 24-aa peptides of fungal and bacterial type 1 NLPs were also able to trigger immunity in Arabidopsis. The widespread phylogenetic distribution of type 1 NLPs makes this protein family (to our knowledge) the first proteinaceous MAMP identified in three different kingdoms of life.
authors.affiliation: Plant-Microbe Interactions, Department of Biology, Utrecht University, 3584 CH Utrecht, The Netherlands; Centre for BioSystems Genomics, 6700 AB Wageningen, The Netherlands; and.
authors.forename: Stan
authors.initials: S
authors.lastname: Oome
authors.affiliation: Plant-Microbe Interactions, Department of Biology, Utrecht University, 3584 CH Utrecht, The Netherlands;
authors.forename: Tom M
authors.initials: TM
authors.lastname: Raaymakers
authors.affiliation: Plant-Microbe Interactions, Department of Biology, Utrecht University, 3584 CH Utrecht, The Netherlands;
authors.forename: Adriana
authors.initials: A
authors.lastname: Cabral
authors.affiliation: Plant-Microbe Interactions, Department of Biology, Utrecht University, 3584 CH Utrecht, The Netherlands;
authors.forename: Simon
authors.initials: S
authors.lastname: Samwel
authors.affiliation: Zentrum für Molekularbiologie der Pflanzen-Pflanzenbiochemie, Eberhard-Karls-Universität Tübingen, D-72076 Tübingen, Germany.
authors.forename: Hannah
authors.initials: H
authors.lastname: Böhm
authors.affiliation: Zentrum für Molekularbiologie der Pflanzen-Pflanzenbiochemie, Eberhard-Karls-Universität Tübingen, D-72076 Tübingen, Germany.
authors.forename: Isabell
authors.initials: I
authors.lastname: Albert
authors.affiliation: Zentrum für Molekularbiologie der Pflanzen-Pflanzenbiochemie, Eberhard-Karls-Universität Tübingen, D-72076 Tübingen, Germany.
authors.forename: Thorsten
authors.initials: T
authors.lastname: Nürnberger
authors.affiliation: Plant-Microbe Interactions, Department of Biology, Utrecht University, 3584 CH Utrecht, The Netherlands; Centre for BioSystems Genomics, 6700 AB Wageningen, The Netherlands; and g.vandenackerveken@uu.nl.
authors.forename: Guido
authors.identifier: http://orcid.org/0000-0002-0183-8978
authors.initials: G
authors.lastname: Van den Ackerveken
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000276:immunology / Q000378:metabolism* / Q000382:microbiology; D008969:Molecular Sequence Data; D011506:Proteins / Q000737:chemistry / Q000145:classification / Q000502:physiology*; D017386:Sequence Homology, Amino Acid
chemical_list: D011506:Proteins
keywords: Nep1-like protein; biotrophic pathogen; microbe-associated molecular pattern; plant immunity; plant-associated microbe