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

Abstract

Summary 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.

The relationship between microbial population size and disease in the Arabidopsis thaliana phyllosphere

“…For the P. syringae analysis, we performed controlled infections in the laboratory of the A. thaliana reference accession Col-0 with two P. syringae strains: Pst DC3000:avrB, which is recognized by the host immune system of this accession 30 , and Pst DC3000:EV, which is not 31 . The formal plant pathology terms for these are incompatible and compatible interactions 32,33 .…”

Defining essential processes in plant pathogenesis with Pseudomonas syringae pv. tomato DC3000 disarmed polymutants and a subset of key type III effectors

“…Amongst the key T3Es, AvrPto, AvrPtoB, HopM1 and HopAM1 can elicit apparent ETI in resistant plants, although responses involving HopM1 and HopAM1 are not well understood (Baltrus et al ., ; Iakovidis et al ., ; Velasquez et al ., ) (Table ). When delivered individually by a P. syringae T3SS or expressed transgenically in plants, HopM1, AvrE1 and HopAM1 also have a capacity to elicit cell death in susceptible hosts, but the relationship of this response to ETI is also unclear (Cunnac et al ., ; Lindeberg et al ., ; Wei et al ., ; Wroblewski et al ., ).…”

“…HopG1 Mukhtar et al, 2011;Shimono et al, 2016;Ustun et al, 2016). HopAM1 (Cunnac et al, 2011;Goel et al, 2008;Iakovidis et al, 2016;Velasquez et al, 2017).…”

Arabidopsis thaliana natural variation in temperature-modulated immunity uncovers transcription factor UNE12 as a thermoresponsive regulator

“…3c), clearly expose a contribution of SA-independent processes to variation in resistance to virulent bacteria, as also indicated by a screen of 1041 A. thaliana accessions in response to spray-inoculated Pst DC3000 63 . High humidity levels used in that screen affected plant stomatal and post-stomatal immune responses 63, 64 and might explain why Mz-0, the most resistant accession in our hands (Fig. 3b), was not identified there.…”