title: Zinc hyperaccumulation substitutes for defense failures beyond salicylate and jasmonate signaling pathways of Alternaria brassicicola attack in Noccaea caerulescens.
abstract: The hypothesis of metal defense as a substitute for a defective biotic stress signaling system in metal hyperaccumulators was tested using the pathosystem Alternaria brassicicola-Noccaea caerulescens under low (2 µM), medium (12 µM) and high (102 µM) Zn supply. Regardless the Zn supply, N. caerulescens responded to fungal attack with the activation of both HMA4 coding for a Zn transporter, and biotic stress signaling pathways. Salicylate, jasmonate, abscisic acid and indoleacetic acid concentrations, as well as biotic stress marker genes (PDF1.2, CHIB, LOX2, PR1 and BGL2) were activated 24 h upon inoculation. Based on the activation of defense genes 24 h after the inoculation an incompatible fungal-plant interaction could be predicted. Nonetheless, in the longer term (7 days) no effective protection against A. brassicicola was achieved in plants exposed to low and medium Zn supply. After 1 week the biotic stress markers were even further increased in these plants, and this compatible interaction was apparently not caused by a failure in the signaling of the fungal attack, but due to the lack of specificity in the type of the activated defense mechanisms. Only plants receiving high Zn exhibited an incompatible fungal interaction. High Zn accumulation in these plants, possibly in cooperation with high glucosinolate concentrations, substituted for the ineffective defense system and the interaction turned into incompatible. In a threshold-type response, these joint effects efficiently hampered fungal spread and, consequently decreased the biotic stress signaling.
authors.affiliation: Plant Physiology Laboratory, Bioscience Faculty, Universitat Autònoma de Barcelona, Bellaterra, E-08193, Spain.
authors.forename: Berta
authors.initials: B
authors.lastname: Gallego
authors.affiliation: Plant Physiology Laboratory, Bioscience Faculty, Universitat Autònoma de Barcelona, Bellaterra, E-08193, Spain.
authors.forename: Soledad
authors.initials: S
authors.lastname: Martos
authors.affiliation: Biology Department, Universitat de les Illes Balears, Palma de Mallorca, E-07122, Spain.
authors.forename: Catalina
authors.initials: C
authors.lastname: Cabot
authors.affiliation: Plant Physiology Laboratory, Bioscience Faculty, Universitat Autònoma de Barcelona, Bellaterra, E-08193, Spain.
authors.forename: Juan
authors.initials: J
authors.lastname: Barceló
authors.affiliation: Plant Physiology Laboratory, Bioscience Faculty, Universitat Autònoma de Barcelona, Bellaterra, E-08193, Spain.
authors.forename: Charlotte
authors.initials: C
authors.lastname: Poschenrieder
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism; D000528:Alternaria / Q000502:physiology*; D019607:Brassicaceae / Q000187:drug effects / Q000276:immunology* / Q000382:microbiology*; D003517:Cyclopentanes / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant; D005961:Glucosinolates / Q000378:metabolism; D054883:Oxylipins / Q000378:metabolism*; D010935:Plant Diseases / Q000235:genetics / Q000276:immunology / Q000382:microbiology; D010937:Plant Growth Regulators / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000378:metabolism; D018520:Plant Shoots / Q000187:drug effects / Q000378:metabolism; D012459:Salicylates / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D015032:Zinc / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D003517:Cyclopentanes; D005961:Glucosinolates; D054883:Oxylipins; D010937:Plant Growth Regulators; D012459:Salicylates; C011006:jasmonic acid; D000040:Abscisic Acid; D015032:Zinc