title: Membrane-targeted HrpNEa can modulate apple defense gene expression.
abstract: Fire blight caused by Erwinia amylovora is the major bacterial disease of tribe Maleae, including apple. Among the proteins secreted by this bacterium, HrpNEa, also called harpin, is known to induce hypersensitive response in nonhost plants and to form amyloid oligomers leading to pore opening in the plasma membrane and alteration of membrane homeostasis. To better understand the physiological effects of HrpNEa in the host plant, we produced transgenic apple plants expressing HrpNEa with or without a secretion signal peptide (SP). HrpNEa expressed with a SP was found to be associated within the membrane fraction, in accordance with amyloidogenic properties and the presence of transmembrane domains revealed by in silico analysis. Expression analysis of 28 apple defense-related genes revealed gene modulations in the transgenic line expressing membrane-targeted HrpNEa. While apple transgenic trees displaying a high constitutive expression level of SP-HrpNEa showed a slight reduction of infection frequency after E. amylovora inoculation, there was no decrease in the disease severity. Thus HrpNEa seems to act as an elicitor of host defenses, when localized in the host membrane.
authors.forename: E
authors.initials: E
authors.lastname: Vergne
authors.forename: T Dugé
authors.initials: TD
authors.lastname: de Bernonville
authors.forename: F
authors.initials: F
authors.lastname: Dupuis
authors.forename: S
authors.initials: S
authors.lastname: Sourice
authors.forename: R
authors.initials: R
authors.lastname: Cournol
authors.forename: P
authors.initials: P
authors.lastname: Berthelot
authors.forename: M A
authors.initials: MA
authors.lastname: Barny
authors.forename: M N
authors.initials: MN
authors.lastname: Brisset
authors.forename: E
authors.initials: E
authors.lastname: Chevreau
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D016000:Cluster Analysis; D044084:Erwinia amylovora / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D027845:Malus / Q000235:genetics / Q000276:immunology* / Q000382:microbiology; D010935:Plant Diseases / Q000276:immunology* / Q000382:microbiology; D057865:Plant Immunity; D018515:Plant Leaves / Q000235:genetics / Q000276:immunology / Q000382:microbiology; D030821:Plants, Genetically Modified; D021382:Protein Sorting Signals; D017434:Protein Structure, Tertiary; D019076:Transgenes
chemical_list: D001425:Bacterial Outer Membrane Proteins; D021382:Protein Sorting Signals; C075462:harpin protein, Erwinia amylovora