title: A porin-like protein from oral secretions of Spodoptera littoralis larvae induces defense-related early events in plant leaves.
abstract: Insect herbivory on plants is a complex incident consisting of at least two different aspects, namely mechanical damage and chemical challenge, as feeding insects introduce oral secretions (OS) into the wounded tissue of the attacked plant. Mechanical wounding alone is sufficient to induce a set of defense-related reactions in host plants, but some early events such as membrane potential (Vm) changes and cytosolic Ca²⁺-elevations can be triggered only by herbivores suggesting that OS-derived molecules are involved in those processes. Following an assay-guided purification based on planar lipid bilayer membrane technique in combination with proteomic analysis, a porin-like protein (PLP) of most likely bacterial origin was determined from collected OS of Spodoptera littoralis larvae. PLP exhibited channel-forming activity. Further, early defense-related events in plant-insect interaction were evaluated by using a purified fraction and α-hemolysin (α-HL) as a commercial pore-forming compound. Both up-regulated the calmodulin-like CML42 in Arabidopsis thaliana, which only responds to oral secretion and not to wounding. An elevation of in vivo [Ca²⁺](cyt) was not observed. Because membrane channel formation is a widespread phenomenon in plant-insect interactions, this PLP might represent an example for microbial compounds from the insect gut which are initially involved in plant-insect interactions.
authors.affiliation: Bioorganic Chemistry Department, Max Planck Institute for Chemical Ecology, Hans-Knöll-Str. 8, D-07745 Jena, Germany.
authors.forename: Huijuan
authors.initials: H
authors.lastname: Guo
authors.forename: Natalie
authors.initials: N
authors.lastname: Wielsch
authors.forename: Jens B
authors.initials: JB
authors.lastname: Hafke
authors.forename: Aleš
authors.initials: A
authors.lastname: Svatoš
authors.forename: Axel
authors.initials: A
authors.lastname: Mithöfer
authors.forename: Wilhelm
authors.initials: W
authors.lastname: Boland
mesh_terms: D000818:Animals; D017360:Arabidopsis / Q000235:genetics* / Q000276:immunology / Q000469:parasitology; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000276:immunology; D002118:Calcium / Q000378:metabolism; D060434:Herbivory / Q000235:genetics / Q000502:physiology; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism*; D052139:Intracellular Calcium-Sensing Proteins / Q000235:genetics* / Q000276:immunology; D007814:Larva / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D018515:Plant Leaves / Q000235:genetics* / Q000276:immunology / Q000469:parasitology; D018411:Spodoptera / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; C575861:CML42 protein, Arabidopsis; D019476:Insect Proteins; D052139:Intracellular Calcium-Sensing Proteins; D002118:Calcium
keywords: Calmodulin-like protein; Cytosolic Ca(2+) concentrations; Oral secretion; Planar lipid bilayer; Plant electrical signals; Porin-like protein