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A root-based N-hydroxypipecolic acid standby circuit to direct immunity and growth of Arabidopsis shoots

Summary

Plants communicate with their shoots through chemical signals produced in their roots when soil microorganisms are present. Researchers discovered that a molecule called N-hydroxypipecolic acid acts like an on-off switch controlled by two proteins, FMO1 and UGT76B1. Beneficial fungi suppress the ‘off’ switch, allowing this signal to travel to leaves where it boosts immunity against disease. Different amounts of this signal have different effects: small amounts help the plant grow, while large amounts strengthen defenses but slow growth.

Background

Soil-borne microorganisms can systemically affect shoot resistance to pathogens through jasmonic acid and salicylic acid signaling. However, the root-derived triggers initiating these systemic responses remain poorly understood. This study investigates the role of N-hydroxypipecolic acid (NHP) as a root signal in mediating plant-microbe interactions.

Objective

To identify and characterize the molecular mechanisms by which root-associated microorganisms trigger systemic resistance and growth changes in Arabidopsis shoots. The study aims to determine whether NHP serves as a long-distance root-to-shoot signal and how its availability is regulated.

Results

NHP is continuously synthesized by FMO1 and simultaneously glucosylated and immobilized by UGT76B1 in roots, creating a ‘standby circuit.’ Root-associated microorganisms modulate this circuit by suppressing UGT76B1 and/or inducing FMO1, releasing varying amounts of NHP to shoots. Different NHP levels dosage-dependently affect both immunity and growth, with low levels promoting growth and moderate immunity, while high levels suppress growth but enhance defense.

Conclusion

This study reveals that root microorganisms exploit a constitutive NHP biosynthesis and inactivation circuit to differentially regulate shoot immunity and growth. The FMO1/UGT76B1 module provides a mechanistic link between root-microbe interactions and systemic plant responses, integrating microbial signals to modulate distant shoot phenotypes.
  • Published in:Nature Plants,
  • Study Type:Experimental Research,
  • Source: PMID: 40696005, DOI: 10.1038/s41477-025-02053-2
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