N-Hydroxy pipecolic acid methyl ester is involved in Arabidopsis immunity

Abstract

The biosynthesis of N-hydroxy pipecolic acid (NHP) has been intensively studied, though knowledge on its metabolic turnover is still scarce. To close this gap, we discovered three novel metabolites via metabolite fingerprinting in Arabidopsis thaliana leaves after Pseudomonas infection and UV-C treatment. Exact mass information and fragmentation by tandem mass spectrometry (MSMS) suggest a methylated derivative of NHP (MeNHP), a NHP-OGlc-hexosyl conjugate (NHP-OGlc-Hex) and an additional NHP-OGlc-derivative. All three compounds were formed in wildtype leaves but were not present in the NHP deficient mutant fmo1-1. The identification of these novel NHP-based molecules was possible by a dual-infiltration experiment using a mixture of authentic NHP- and D9-NHP-standards for leaf infiltration followed by an UV-C treatment. Interestingly, the signal intensity of MeNHP and other NHP-derived metabolites increased in ugt76b11 mutant plants. This suggests a detour, for the inability to synthesize NHP-O-glucoside. For MeNHP, we unequivocally determined the site of methylation at the carboxylic acid function. MeNHP application by leaf infiltration leads to the detection of a MeNHP-OGlc as well as NHP, suggesting MeNHP-hydrolysis to NHP. This is in line with the observation that MeNHP-infiltration is able to rescue the fmo1-1 susceptible phenotype against Hyaloperonospora arabidopsidis Noco 2. Together these data suggest MeNHP as additional storage or transport form of NHP.

Dynamic Changes in Plant Secondary Metabolites Induced by Botrytis cinerea Infection

“…The Lys catabolite pipecolic acid (Pip) is a critical metabolic mediator of several forms of inducible resistance in Arabidopsis, which accumulates following pathogen recognition [ 45 ]. Then, N-hydroxypipecolic acid (NHP) is the actual regulator of SAR rather than Pip [ 46 , 47 ]. This result was consistent with the downregulated Pip in the leaves of the treated group compared to the non-treated group, probably attributable to hydroxylation of Pip to NHP.…”

Verticillium dahliae Vta3 promotes ELV1 virulence factor gene expression in xylem sap, but tames Mtf1-mediated late stages of fungus-plant interactions and microsclerotia formation

“…Leaves from tomato plant infection experiments were harvested at 21 dpi, frozen and ground in liquid nitrogen. Phytohormone extraction with 80% methanol was performed on approximately 50 mg (fresh weight) ground material [ 48 ]. Pipecolic acid (Pip) and salicylic acid (SA) were reversed phase-separated using an ACQUITY UPLC system (Waters) and analyzed by nanoelectrospray ionization (TriVersa Nanomate, Advion BioSciences) coupled with an AB Sciex 4000 QTRAP tandem mass spectrometer (AB Sciex) employed in scheduled multiple reaction monitoring mode as described [ 49 ].…”

Specialized metabolite modifications in Brassicaceae seeds and plants: diversity, functions and related enzymes

“…143 Moreover, N-hydroxy-pipecolic was also found to contribute to plant enhanced resistance during P. syringae infection and the mechanism of glycosylation mediated by UGT76B1 was determined as crucial for balancing growth and defence. 144,146 Similarly, UGT74F2 loss of function mutant led to enhanced resistance to the biotrophic pathogen P. syringae while the loss of function of the close relative UGT74F1 gene decreased the susceptibility to the same bacterial pathogen. 145 Hence, salicylic acid (SA) exists in an active form (free state) in plant cells and in an inactive storage glycosylated state within cell vacuoles, also known as SA glucoside (SAG) and SA glucose ester (SGE).…”