Zinc triggers signaling mechanisms and defense responses promoting resistance to Alternaria brassicicola in Arabidopsis thaliana.
According to the elemental defense hypothesis the accumulation of trace elements by plants may substitute for organic defenses, while the joint effects hypothesis proposes that trace elements and organic defenses can have additive or synergistic effects against pathogens or herbivores. To evaluate these hypotheses the response of the pathosystem Alternaria brassicicola-Arabidopsis thaliana to control (2μM) and surplus (12μM) Zn was evaluated using the camalexin deficient mutant pad3-1 and mtp1-1, a mutant with impaired Zn vacuolar storage, along with the corresponding wildtypes. In vitro, a 50% inhibition of fungal growth was achieved by 440μM Zn. A. thaliana leaves could accumulate equivalent concentrations without harm. In fact, surplus Zn enhanced the resistance of A. thaliana to fungal attack in Columbia (Col-0), Wassilewskija (WS), and mtp1-1. However, surplus Zn was unable to protect pad3-1 demonstrating that Zn cannot substitute for camalexin, the main organic defense in A. thaliana. High, non phytotoxic leaf Zn concentrations enhanced the resistance to A. brassicicola of A. thaliana genotypes able to produce camalexin. This was mainly due to Zn-induced enhancement of the JA/ETH signaling pathway leading to enhanced PAD3 expression. These results support the joint effects hypothesis and highlight the importance of adequate Zn supply for reinforced pathogen resistance.
Plant Physiology Laboratory, Bioscience Faculty, C/de la Vall Moronta s.n., Universitat Autònoma de Barcelona, E-08193 Bellaterra, Spain. Electronic address: Soledad.martos@uab.cat.
Soledad
S
Martos
Plant Physiology Laboratory, Bioscience Faculty, C/de la Vall Moronta s.n., Universitat Autònoma de Barcelona, E-08193 Bellaterra, Spain. Electronic address: bertagallego@gmail.com.
Berta
B
Gallego
Biology Department, Universitat de les Illes Balears, Carretera Valldemossa km 7.5, E-07122 Palma de Mallorca, Spain. Electronic address: ccabot@uib.es.
Catalina
C
Cabot
Plant Physiology Laboratory, Bioscience Faculty, C/de la Vall Moronta s.n., Universitat Autònoma de Barcelona, E-08193 Bellaterra, Spain. Electronic address: merce.llugany@uab.cat.
Mercè
M
Llugany
Plant Physiology Laboratory, Bioscience Faculty, C/de la Vall Moronta s.n., Universitat Autònoma de Barcelona, E-08193 Bellaterra, Spain. Electronic address: juan.barcelo@uab.es.
Juan
J
Barceló
Plant Physiology Laboratory, Bioscience Faculty, C/de la Vall Moronta s.n., Universitat Autònoma de Barcelona, E-08193 Bellaterra, Spain. Electronic address: Charlotte.poschenrieder@uab.es.
Charlotte
C
Poschenrieder
D000528:Alternaria / Q000502:physiology*; D017360:Arabidopsis / Q000235:genetics / Q000382:microbiology / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D060467:Disease Resistance; D020869:Gene Expression Profiling; D010935:Plant Diseases / Q000382:microbiology; D015398:Signal Transduction; D013312:Stress, Physiological; D015032:Zinc / Q000378:metabolism / Q000502:physiology*
D029681:Arabidopsis Proteins; D027682:Cation Transport Proteins; D015032:Zinc; C500829:ZAT protein, Arabidopsis
Alternaria brassicicola; Arabidopsis thaliana; Camalexin; Metal defense; Necrotrophic fungal infection; Zn transporters