N-hydroxy-pipecolic acid is a mobile signal that induces systemic disease resistance in Arabidopsis

Abstract

20Systemic acquired resistance (SAR) is a global response in plants induced at the site of 21 infection that leads to long-lasting and broad-spectrum disease resistance at distal, 22 uninfected tissues. Despite the importance of this priming mechanism, the identity of the 23 mobile defense signal that moves systemically throughout plants to initiate SAR has 24 remained elusive. In this paper, we describe a new metabolite, N-hydroxy-pipecolic acid 25 (N-OH-Pip), and provide evidence that this molecule is a mobile signal that plays a 26 central role in initiating SAR signal transduction in Arabidopsis thaliana. We 27 demonstrate that FLAVIN-DEPENDENT MONOOXYGENASE 1 (FMO1), a key 28 regulator of SAR-associated defense priming, can synthesize N-OH-Pip from pipecolic 29 acid in planta, and exogenously applied N-OH-PIP moves systemically in Arabidopsis 30 and can rescue the SAR-deficiency of fmo1 mutants. We also demonstrate that N-OH-31 Pip treatment causes systemic changes in the expression of pathogenesis-related 32 genes and metabolic pathways throughout the plant, and enhances resistance to a 33 bacterial pathogen. This work provides new insight into the chemical nature of a mobile 34 signal for SAR and also suggests that the N-OH-Pip pathway is a promising target for 35 metabolic engineering to enhance disease resistance. 36 37the establishment of SAR signaling [10, 12, 13]. The biochemical function of FMO1 has 68 remained unknown. 69Several forward genetic screens searching for SAR-deficient mutants identified 70 multiple alleles of fmo1, ald1 (AGD2-LIKE DEFENSE RESPONSE PROTEIN 1), and 71 sard4 (SAR-DEFICIENT 4), highlighting the importance of metabolites produced by 72 these enzymes [16, 17, 19, 20]. ALD1 and SARD4 are involved in the biosynthesis of 73 Pip [13, 21, 22]. Irrigation of wild type Arabidopsis plants with Pip induces SAR [13], 74 which suggested that Pip might be a mobile SAR metabolite. Navarova et al. reported, 75 however, that Pip could not trigger SAR in fmo1 mutants [13]. In addition, fmo1 plants 76 accumulate high levels of Pip during a late stage of infection compared to wild-type 77 plants [13]. These findings feature FMO1 as a key missing link in the mechanism of Pip-78 associated SAR. 79 We and others have found untargeted metabolite analysis of Arabidopsis genetic 80 mutants to be a powerful approach for the identification of small molecules associated 81 with fitness phenotypes (either previously characterized or suggested by transcriptome 82 analysis) [23]. Examples include the identification and characterization of cytochromes 83 P450 involved in phytoalexin production [24] and iron acquisition [25]. Given that FMO1 84 is one of the genes most responsive to biotic stress (as indicated by analysis of 85 previously reported Arabidopsis microarray data summarized in Fig. S9), and that 86 genetic data suggest molecules generated by FMO1 are required for initiating SAR [16-87 18], we sought to apply an untargeted metabolomics approach to determine the 88 products of FMO1 and their ...

High‐resolution expression profiling of selected gene sets during plant immune activation

“…We selected investigated 35 ERGs, and also 17 non-ERGs as controls, based on their transcriptional regulation patterns (Figure S1A; Table S2) . The ERGs include genes that are important for conferring full resistance to various plant pathogens and are involved in the biosynthesis of phytohormones, salicylic acid (SA) and pipecolic acid (Pip), including ICS1, EDS5, PBS3, FMO1 and genes that encode the transcription factors (TFs) WRKY51 and SARD1 (Wildermuth et al, 2001;Nawrath et al, 2002;Nobuta et al, 2007;Zhang et al, 2010;Wang et al, 2011;Hartmann et al, 2018;Chen et al, 2018;Gao et al, 2011). Non-ERG control genes include UBQ10 and ACT7, as well as late immune response genes , such as PR1, which is known to be activated by elevated SA (Cao et al, 1997).…”

Signals of Systemic Immunity in Plants: Progress and Open Questions

“…In two very recent publications, added in proof, a new SAR signalling compound, FMO1-dependent N-oxygenation product of Pip, N-hydroxypipecolic acid (NHS) was described ( Figure 1 ) [ 110 , 111 ].…”

High-resolution Expression Profiling of Selected Gene Sets during Plant Immune Activation

“…We selected investigated 35 ERGs, and also 17 non‐ERGs as controls, based on their transcriptional regulation patterns (Figure S1A; Table S2) (Sohn et al, ). The ERGs include genes that are important for conferring full resistance to various plant pathogens and are involved in the biosynthesis of phytohormones, salicylic acid (SA) and pipecolic acid (Pip), including ICS1 , EDS5, PBS3, FMO1 and genes that encode the transcription factors (TFs) WRKY51 and SARD1 (Wildermuth et al, ; Nawrath et al, ; Nobuta et al, ; Zhang et al, ; Wang et al, ; Hartmann et al, ; Chen et al, ; Gao et al, ). Non‐ERG control genes include UBQ10 and ACT7 , as well as late immune response genes (Sohn et al, ), such as PR1 , which is known to be activated by elevated SA (Cao et al, ).…”