title: The Poplar Rust-Induced Secreted Protein (RISP) Inhibits the Growth of the Leaf Rust Pathogen Melampsora larici-populina and Triggers Cell Culture Alkalinisation.
abstract: Plant cells secrete a wide range of proteins in extracellular spaces in response to pathogen attack. The poplar rust-induced secreted protein (RISP) is a small cationic protein of unknown function that was identified as the most induced gene in poplar leaves during immune responses to the leaf rust pathogen Melampsora larici-populina, an obligate biotrophic parasite. Here, we combined in planta and in vitro molecular biology approaches to tackle the function of RISP. Using a RISP-mCherry fusion transiently expressed in Nicotiana benthamiana leaves, we demonstrated that RISP is secreted into the apoplast. A recombinant RISP specifically binds to M. larici-populina urediniospores and inhibits their germination. It also arrests the growth of the fungus in vitro and on poplar leaves. Interestingly, RISP also triggers poplar cell culture alkalinisation and is cleaved at the C-terminus by a plant-encoded mechanism. Altogether our results indicate that RISP is an antifungal protein that has the ability to trigger cellular responses.
authors.affiliation: Institut National de la Recherche Agronomique, Centre INRA Nancy Lorraine, UMR 1136 Interactions Arbres/MicroorganismesChampenoux, France; Faculté des Sciences et Technologies, UMR 1136 Interactions Arbres/Microorganismes, Université de LorraineVandoeuvre-lès-Nancy, France; The Sainsbury LaboratoryNorwich, UK.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Petre
authors.affiliation: Institut National de la Recherche Agronomique, Centre INRA Nancy Lorraine, UMR 1136 Interactions Arbres/MicroorganismesChampenoux, France; Faculté des Sciences et Technologies, UMR 1136 Interactions Arbres/Microorganismes, Université de LorraineVandoeuvre-lès-Nancy, France.
authors.forename: Arnaud
authors.initials: A
authors.lastname: Hecker
authors.affiliation: Groupe de Recherche en Biologie Végétale, Université du Québec à Trois-Rivières, Trois-Rivières QC, Canada.
authors.forename: Hugo
authors.initials: H
authors.lastname: Germain
authors.affiliation: CRM2, Equipe BioMod, Faculté des Sciences et Technologies, UMR 7036, Université de LorraineVandoeuvre-lès-Nancy, France; CNRS, CRM2, Equipe BioMod, Faculté des Sciences et Technologies, UMR 7036Vandoeuvre-lès-Nancy, France.
authors.forename: Pascale
authors.initials: P
authors.lastname: Tsan
authors.affiliation: The Sainsbury Laboratory Norwich, UK.
authors.forename: Jan
authors.initials: J
authors.lastname: Sklenar
authors.affiliation: Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, Québec QC, Canada.
authors.forename: Gervais
authors.initials: G
authors.lastname: Pelletier
authors.affiliation: Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, Québec QC, Canada.
authors.forename: Armand
authors.initials: A
authors.lastname: Séguin
authors.affiliation: Institut National de la Recherche Agronomique, Centre INRA Nancy Lorraine, UMR 1136 Interactions Arbres/MicroorganismesChampenoux, France; Faculté des Sciences et Technologies, UMR 1136 Interactions Arbres/Microorganismes, Université de LorraineVandoeuvre-lès-Nancy, France.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Duplessis
authors.affiliation: Institut National de la Recherche Agronomique, Centre INRA Nancy Lorraine, UMR 1136 Interactions Arbres/MicroorganismesChampenoux, France; Faculté des Sciences et Technologies, UMR 1136 Interactions Arbres/Microorganismes, Université de LorraineVandoeuvre-lès-Nancy, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Rouhier
keywords: Populus trichocarpa; antifungal activity; obligate biotroph; peptide elicitor; plant immunity; rust fungus