<i>N</i>-hydroxy-pipecolic acid is a mobile metabolite that induces systemic disease resistance in <i>Arabidopsis</i>.

Abstract

Systemic acquired resistance (SAR) is a global response in plants induced at the site of infection that leads to long-lasting and broad-spectrum disease resistance at distal, uninfected tissues. Despite the importance of this priming mechanism, the identity and complexity of defense signals that are required to initiate SAR signaling is not well understood. In this paper, we describe a metabolite, <i>N</i>-hydroxy-pipecolic acid (<i>N</i>-OH-Pip) and provide evidence that this mobile molecule plays a role in initiating SAR signal transduction in <i>Arabidopsis thaliana</i> We demonstrate that FLAVIN-DEPENDENT MONOOXYGENASE 1 (FMO1), a key regulator of SAR-associated defense priming, can synthesize <i>N</i>-OH-Pip from pipecolic acid <i>in planta</i>, and exogenously applied <i>N</i>-OH-Pip moves systemically in <i>Arabidopsis</i> and can rescue the SAR-deficiency of <i>fmo1</i> mutants. We also demonstrate that <i>N</i>-OH-Pip treatment causes systemic changes in the expression of pathogenesis-related genes and metabolic pathways throughout the plant and enhances resistance to a bacterial pathogen. This work provides insight into the chemical nature of a signal for SAR and also suggests that the <i>N</i>-OH-Pip pathway is a promising target for metabolic engineering to enhance disease resistance.