Work

Systemic acquired resistance signaling molecule N-hydroxypipecolic acid is involved in Age-related resistance in Arabidopsis thaliana

Year: 2026

Type: article

Abstract: Little is known about how mature Arabidopsis thaliana (Arabidopsis) plants become competent to initiate age-related resistance to normally virulent Pseudomonas syringae pv. tomato (Pst). RNA sequencing was used to identify genes that contribute to age-related resistance by comparing the response to Pst in young, susceptible plants 3.5 weeks postgermination with mature Age-related resistance-competent plants 6 weeks postgermination. Comparative transcriptomics revealed that age-related resistance shares many genes with pathogen-associated molecular pattern-triggered immunity, effector-triggered immunity, and systemic acquired resistance, providing additional evidence for the emerging idea that plant immune pathways are intertwined and interconnected. Age-related resistance-responding leaves expressed genes for the biosynthesis of N-hydroxypipecolic acid, a signaling molecule involved in systemic acquired resistance during the establishment of a primed state in systemic leaves. N-hydroxypipecolic acid biosynthesis mutants (ald1-1, fmo1-1) had age-related resistance defects and accumulated less intercellular salicylic acid than wild-type Col-0, indicating a requirement for functional N-hydroxypipecolic acid biosynthesis genes for intercellular salicylic acid accumulation during age-related resistance. Salicylic acid perception by NPR1/4 proteins was required for age-related resistance, as demonstrated by the age-related resistance-defective phenotype of the salicylic acid-signaling mutant, npr1-1 npr4-4D. N-hydroxypipecolic acid biosynthesis genes were still expressed in npr1-1 npr4-4D, suggesting that, similar to systemic acquired resistance, N-hydroxypipecolic acid functions upstream of NPR1-mediated signaling during age-related resistance. Unlike age-related resistance-incompetent plants (3, 4, 5 weeks postgermination untreated), age-related resistance-competent plants (6 weeks postgermination untreated) expressed N-hydroxypipecolic acid biosynthesis genes, accumulated N-hydroxypipecolic acid, and expressed immunity-associated cell surface receptors RLP23 and RLP28, supporting the idea that N-hydroxypipecolic acid contributes to initiating a developmentally controlled age-related resistance-competent primed state in mature Arabidopsis that is similar to the primed state established in distant leaves during systemic acquired resistance.

Source: PLANT PHYSIOLOGY

DOI: 10.1093/plphys/kiag302