Tracking Azelaic Acid defense signal to Boost Plant Disease Resistance

Scientists have developed a protocol for analyzing the movement and uptake of isotopically labeled azelaic acid in the model plant Arabidopsis thaliana, providing valuable insights into plant immune responses. This research is particularly significant for understanding how plants trigger systemic resistance against pathogens. The protocol, detailed by Dr. Nicolás Cecchini, Dr. Suruchi Roychoudhry, and Professor Jean Greenberg, focuses on studying the defense signal azelaic acid, a molecule that travels within the plant, triggering systemic resistance in tissues distant from the site of infection.

Professor Jean Greenberg from the University of Chicago and Dr. Nicolás Cecchini from the University of Córdoba spearheaded this work, which was published in the STAR Protocols journal. The researchers devised methods to measure azelaic acid movement from leaves to other parts of the plant and its uptake into leaf discs. “Understanding the generation, movement, uptake, and perception of mobile defense signals is key for unraveling the systemic resistance programs in flowering plants against pathogens,” said Professor Greenberg, explaining the rationale behind their study.

The team utilized radiolabeled azelaic acid, a version of azelaic acid labeled with carbon-14, to trace its movement within the plant. This compound was applied to a single leaf, and the researchers tracked its travel to both aerial and root tissues, providing critical information on how plants mobilize their defense signals. One notable result was the movement of azelaic acid from the treated leaf to distal tissues, offering insight into how the plant coordinates its immune response across various organs. Additionally, a control experiment using radiolabeled sucrose helped distinguish azelaic acid-specific movement from general transport issues in the plant’s phloematic system.

The researchers extended the study by analyzing azelaic acid uptake into leaf discs, where they applied the radiolabeled azelaic acid and observed its absorption into the tissue. They further explored the potential for root-to-shoot transport using deuterium-labeled azelaic acid, a version of azelaic acid labeled with deuterium. These methods open up new avenues for investigating how plants mobilize defense signals from roots to shoots, thus providing comprehensive insights into their immune systems.

The use of isotopically labeled azelaic acid has several advantages, particularly its high sensitivity in detecting even small quantities of the molecule moving within the plant. However, as Dr. Cecchini noted, there are challenges associated with using radioactive materials. “We can trace the movement of radiolabeled molecules, but specialized techniques, such as gas chromatography-mass spectrometry (GC-MS), are needed to confirm whether azelaic acid remains intact or has been converted into another form during transport,” he explained.

The study’s findings have profound implications for plant biology, as they advance the understanding of how plants manage to develop long-lasting resistance against pathogens. Systemic resistance, a type of plant immune response, requires signals that move from one part of the plant to another. Azelaic acid plays a crucial role in this process by priming the plant for faster and more effective responses when facing subsequent infections.

Looking forward, these protocols are likely to be adapted for studying other plant species and defense signals. The researchers suggest that their methods could be employed to investigate different small molecules involved in plant immunity, offering a robust toolset for future studies on systemic plant resistance.