N-Hydroxypipecolic acid

N-Hydroxypipecolic acid (N-hydroxypipecolic acid), a plant metabolite, also plays a key role in SAR (systemic acquired resistance) and to a lesser extent in basal resistance.^[1] N-hydroxypipecolic acid requires basal salicylic acid and components of the salicylic acid signaling pathway to induce systemic acquired resistance genes.^[2] N-hydroxypipecolic acid can confer immunity via the salicylic acid receptor NPR1 to reprogram plants at the level of transcription and prime plants for an enhanced defense capacity.^[4]

In vitro experiment it shown that treatment of Arabidopsis Col-0 plants with a 1 mM N-hydroxypipecolic acid solution, either applied via the soil or sprayed on the leaf rosette, triggered a strong SAR response in the leaves.^[3] In addition, when treatment with N-hydroxypipecolic acid in the individual leaves of Col-0 plants, acquired resistance developed not only in the treated leaves but also in distant, systemic leaves.^[5] There is a strong N-hydroxypipecolic acid (1 mM)-mediated priming of the pathogen-triggered accumulation of camalexin. And exogenous N-hydroxypipecolic acid also strongly primed the N-hydroxypipecolic acid-deficient fmo1 mutant for the Psm-triggered accumulation of camalexin. Pretreatment with 1mM N-hydroxypipecolic acid also significantly primed the leaves for an enhanced accumulation of Pip and SA in response to the mock-infiltration, suggesting that N-hydroxypipecolic acid also primes responses to mechanical stress in Arabidopsis.^[6]

References:
[1].Hartmann M, Zeier J. N-hydroxypipecolic acid and salicylic acid: a metabolic duo for systemic acquired resistance. Curr Opin Plant Biol. 2019 Aug;50:44-57.
[2].Nair A, et al. N-hydroxypipecolic acid-induced transcription requires the salicylic acid signaling pathway at basal SA levels. Plant Physiol. 2021 Dec 4;187(4):2803-2819.
[3].Schnake A, et al. Inducible biosynthesis and immune function of the systemic acquired resistance inducer N-hydroxypipecolic acid in monocotyledonous and dicotyledonous plants. J Exp Bot. 2020 Oct 22;71(20):6444-6459.
[4].Zeier J. Metabolic regulation of systemic acquired resistance. Curr Opin Plant Biol. 2021 Aug;62:102050.
[5].Chen YC, et al. N-hydroxy-pipecolic acid is a mobile metabolite that induces systemic disease resistance in Arabidopsis. Proc Natl Acad Sci U S A. 2018 May 22;115(21):E4920-E4929.
[6].Yildiz I, et al. The mobile SAR signal N-hydroxypipecolic acid induces NPR1-dependent transcriptional reprogramming and immune priming. Plant Physiol. 2021 Jul 6;186(3):1679-1705.