LEXINGTON, Ky. — University of Kentucky researchers have identified how a molecular imbalance in plants can undermine their natural defense systems, a finding that could help protect crops from disease. The study, published in Science Advances, reveals that excess nitric oxide disrupts the communication system plants use to warn themselves of pathogen threats.
Plants lacking immune systems comparable to those in animals have evolved an ingenious alternative: when one leaf is attacked by disease, it sends chemical alerts to other parts of the plant, preparing them for infection. This whole-plant immune response is called systemic acquired resistance, or SAR. The breakthrough research, conducted at the Martin-Gatton College of Agriculture, Food and Environment, shows how this critical defense mechanism can fail.
The key to SAR is a molecule called salicylic acid, which is chemically related to aspirin. In healthy plants, salicylic acid travels through cellular transport systems to carry immune warnings from infected leaves to the rest of the organism. But the UK team discovered that when nitric oxide accumulates to excessive levels, it alters the acidity balance around plant cells, creating what postdoctoral scholar Huazhen Liu described as a “pH traffic jam.” The resulting chemical barrier traps the salicylic acid signal before it can reach the plant’s transport network.
Researchers studied laboratory specimens of Arabidopsis, a small plant commonly used in genetic research, focusing on mutants with high nitric oxide levels. When these plants were exposed to pathogens, they failed to activate systemic acquired resistance. However, when researchers delivered salicylic acid directly through the plant’s roots, bypassing the blocked transport route, the immune system responded normally. “It is not enough for a plant to make a defense signal. That signal also has to move,” said Pradeep Kachroo, co-author and an American Association for the Advancement of Science fellow.
The research connects to broader agricultural challenges. Understanding how plants move chemical signals during disease, drought and heat stress could inform new strategies for protecting crops facing constant pressure from pathogens and environmental changes. The findings also suggest that similar signaling principles may apply across living organisms, since nitric oxide affects cellular communication in animals as well.
The work was supported by the U.S. National Science Foundation and the U.S. Department of Agriculture.
This article was generated by AI (claude-haiku-4-5-20251001) based on source material from University of Kentucky News, enriched with 3 web searches. The original source is available at https://uknow.uky.edu/research/uk-researchers-find-excess-nitric-oxide-blocks-plant-immune-signals.
