Diverse mechanisms of resistance to Pseudomonas syringae in a thousand natural accessions of Arabidopsis thaliana

• Published in: The New phytologist 2017-06, Vol.214 (4), p.1673-1687
• Main Authors: Velásquez, André C., Oney, Matthew, Huot, Bethany, Xu, Shu, He, Sheng Yang
• Format: Article
• Language: English
• Subjects: Arabidopsis - microbiology; Arabidopsis - physiology; Arabidopsis thaliana; AvrPto; Bacteria; Bacterial Proteins - metabolism; Biological evolution; Cell Death; coevolution; Defence mechanisms; defense mechanisms; Disease resistance; Disease Resistance - physiology; Ecology; effector‐triggered immunity (ETI); Host-Pathogen Interactions - physiology; hypersensitive response; Infections; Inoculation; Interactions; Microbiological strains; mutants; Mutation; Pathogens; Plant Diseases - microbiology; plant immunity; Plant Leaves - microbiology; plant pathogen; Pseudomonas; Pseudomonas syringae - genetics; Pseudomonas syringae - metabolism; Pseudomonas syringae - pathogenicity; Pseudomonas syringae pv. tomato; Pseudomonas syringae pv. tomato DC3000; Reactive oxygen species; Reactive Oxygen Species - metabolism; Resistance mechanisms; Salicylic acid; salicylic acid (SA); Salicylic Acid - metabolism; Threatened species; Tomatoes
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/nph.14517

Plants are continuously threatened by pathogen attack and, as such, they have evolved mechanisms to evade, escape and defend themselves against pathogens. However, it is not known what types of defense mechanisms a plant would already possess to defend against a potential pathogen that has not co-evolved with the plant. We addressed this important question in a comprehensive manner by studying the responses of 1041 accessions of Arabidopsis thaliana to the foliar pathogen Pseudomonas syringae pv. tomato (Pst) DC3000. We characterized the interaction using a variety of established methods, including different inoculation techniques, bacterial mutant strains, and assays for the hypersensitive response, salicylic acid (SA) accumulation and reactive oxygen species production. Fourteen accessions showed resistance to infection by Pst DC3000. Of these, two accessions had a surface-based mechanism of resistance, six showed a hypersensitive-like response while three had elevated SA levels. Interestingly, A. thaliana was discovered to have a recognition system for the effector AvrPto, and HopAM1 was found to modulate Pst DC3000 resistance in two accessions. Our comprehensive study has significant implications for the understanding of natural disease resistance mechanisms at the species level and for the ecology and evolution of plant–pathogen interactions.