Rhizobacteria-Induced Systemic Priming Against Fungal Pathogens Involves Hydroxycinnamic Acid Amides
Mackenzie Eli William Loranger1, Wolfgang Moeder1, Hyunsuh Lee1
1Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada.
Plant, Cell & Environment
|March 30, 2026
Summary
Rhizosphere bacteria trigger plant immunity (Induced Systemic Resistance, ISR). Scientists found that hydroxycinnamic acid amides (HCAAs) accumulate in plants, directly fighting fungal pathogens and enhancing resistance.
Area of Science:
- Plant Pathology
- Microbiology
- Biochemistry
Background:
- The rhizosphere harbors diverse microbes, distinct from bulk soil.
- Certain rhizosphere bacteria induce plant immunity, known as Induced Systemic Resistance (ISR).
- Understanding ISR mechanisms is crucial for sustainable agriculture and crop protection.
Purpose of the Study:
- To elucidate the metabolic underpinnings of ISR in tomato plants.
- To identify specific metabolites involved in ISR and their functional roles.
- To investigate the contribution of hydroxycinnamic acid amides (HCAAs) to plant defense.
Main Methods:
- Untargeted metabolic profiling of tomato plants treated with ISR-inducing bacteria (Pseudomonas defensor WCS374r and Bacillus velezensis VFb49).
- Identification and quantification of differentially accumulated metabolites (DAMs).
- In vitro antimicrobial assays against fungal pathogens (Botrytis cinerea, Fusarium virguliforme) and genetic analysis in Arabidopsis thaliana.
Main Results:
- Hydroxycinnamic acid amides (HCAAs), specifically caffeoyl putrescine and feruloyl putrescine, were identified as key DAMs.
- These HCAAs demonstrated direct antimicrobial activity against B. cinerea and F. virguliforme.
- The enzyme agmatine coumaroyl transferase (AtACT) was induced by bacteria and essential for resistance, with the MATE transporter AtDTX18 facilitating apoplastic HCAA function.
Conclusions:
- Accumulation of HCAAs is a significant mechanism contributing to ISR-mediated plant defense.
- The study highlights the role of specific metabolites and transporters in plant-microbe interactions and disease resistance.
- Findings provide novel insights into ISR pathways, with potential applications in developing biocontrol strategies.
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