title: Herbivore-induced resistance against microbial pathogens in Arabidopsis.
abstract: Caterpillars of the herbivore Pieris rapae stimulate the production of jasmonic acid (JA) and ethylene (ET) in Arabidopsis (Arabidopsis thaliana) and trigger a defense response that affects insect performance on systemic tissues. To investigate the spectrum of effectiveness of P. rapae-induced resistance, we examined the level of resistance against different pathogens. Although the necrotrophic fungus Alternaria brassicicola is sensitive to JA-dependent defenses, herbivore-induced resistance was not effective against this pathogen. By contrast, caterpillar feeding significantly reduced disease caused by the bacterial pathogens Pseudomonas syringae pv tomato and Xanthomonas campestris pv armoraciae. However, this effect was apparent only locally in caterpillar-damaged tissue. Arabidopsis mutants jar1, coi1, ein2, sid2, eds5, and npr1 showed wild-type levels of P. rapae-induced protection against P. syringae pv tomato, suggesting that this local, herbivore-induced defense response does not depend exclusively on either JA, ET, or salicylic acid (SA). Resistance against the biotroph Turnip crinkle virus (TCV) requires SA, but not JA and ET. Nevertheless, herbivore feeding strongly affected TCV multiplication and TCV lesion formation, also in systemic tissues. Wounding alone was not effective, but application of P. rapae regurgitate onto the wounds induced a similar level of protection. Analysis of SA-induced PATHOGENESIS RELATED-1 (PR-1) expression revealed that P. rapae grazing primed Arabidopsis leaves for augmented expression of SA-dependent defenses. Pharmacological experiments showed that ET acts synergistically on SA-induced PR-1, suggesting that the increased production of ET upon herbivore feeding sensitizes the tissue to respond faster to SA, thereby contributing to an enhanced defensive capacity toward pathogens, such as TCV, that trigger SA-dependent defenses upon infection.
authors.affiliation: Graduate School of Experimental Plant Sciences, Section of Phytopathology, Institute of Environmental Biology, Utrecht University, 3508 TB Utrecht, The Netherlands.
authors.forename: Martin
authors.initials: M
authors.lastname: De Vos
authors.forename: Wendy
authors.initials: W
authors.lastname: Van Zaanen
authors.forename: Annemart
authors.initials: A
authors.lastname: Koornneef
authors.forename: Jerôme P
authors.initials: JP
authors.lastname: Korzelius
authors.forename: Marcel
authors.initials: M
authors.lastname: Dicke
authors.forename: L C
authors.initials: LC
authors.lastname: Van Loon
authors.forename: Corné M J
authors.initials: CM
authors.lastname: Pieterse
mesh_terms: D000528:Alternaria / Q000502:physiology; D000818:Animals; D017360:Arabidopsis / Q000382:microbiology* / Q000502:physiology / Q000821:virology; D002080:Butterflies / Q000502:physiology*; D005247:Feeding Behavior; D007814:Larva / Q000502:physiology*; D010935:Plant Diseases; D018515:Plant Leaves / Q000382:microbiology; D010942:Plant Viruses / Q000502:physiology; D044224:Pseudomonas syringae / Q000502:physiology; D020156:Salicylic Acid / Q000378:metabolism; D016959:Xanthomonas campestris / Q000502:physiology
chemical_list: D020156:Salicylic Acid