The Arabidopsis ISR1 Locus is Required for Rhizobacteria-Mediated Induced Systemic Resistance Against Different Pathogens

Abstract

In Arabidopsis thaliana, non-pathogenic, root-colonizing Pseudomonas fluorescens WCS417r bacteria trigger an induced systemic resistance (ISR) that is phenotypically similar to pathogen-induced systemic acquired resistance (SAR). In contrast to SAR, WCS417r-mediated ISR is controlled by a salicylic acid (SA)-independent signalling pathway that requires an intact response to the plant hormones jasmonic acid (JA) and ethylene (ET). Arabidopsis accessions RLD1 and Ws-0 fail to express ISR against Pseudomonas syringae pv. tomato and show enhanced disease susceptibility to this pathogen. Genetic analysis of progeny from crosses between WCS417r-responsive and non-responsive accessions demonstrated that ISR inducibility and basal resistance against P. syringae pv. tomato are controlled by a single dominant locus (ISR1) on chromosome III (Ton et al., 1999[8]). Here, we investigated the role of the ISR1 locus in ISR, SAR and basal resistance against three additional pathogens: Xanthomonas campestris pv. armoraciae, Peronospora parasitica and turnip crinkle virus (TCV), using accessions Col-0 (ISR1), RLD1 (isr1) and Ws-0 (isr1) as host plants.

Abbreviations

ISR: induced systemic resistance

SAR: systemic acquired resistance

SA: salicylic acid

JA: jasmonic acid

ET: ethylene

Arabidopsis - basal resistance - ethylene - induced systemic resistance - plant defence - Pseudomonas fluorescens - systemic acquired resistance

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Section Editor: J. Draper