When cold and flu season comes around, we take steps like getting our flu shots and taking immune supplements to strengthen our bodies' defenses against pathogens. Plants face pathogenic threats, too. Plant pathogens can have devastating impacts on crop yield, with up to 40% of global food crops lost annually, and such loss has severe implications for food security. But what if we could boost plant immune systems like we do our own, and make them better able to withstand or fend off biological threats? Recently published in Nature Communications Biology, new research from scientists at the Boyce Thompson Institute (BTI) explored this very concept and found that a previously unrecognized natural compound can provide lasting protection against a broad range of plant pathogens.
The research, investigating a class of nematode pheromones called ascarosides, was led by Professor Emeritus Dan Klessig and Professor Frank Schroeder of BTI , together with former BTI postdoc Dr. Murli Manohar (all three are co-founders of the BTI startup Ascribe Bioscience ), and Uwe Conrath, Professor at RWTH Aachen University in Germany.
"My lab previously showed that nematodes, which are ubiquitous in soil and include many plant and animal parasites, produce these simple glycolipids called ascarosides," explained Dr. Schroeder. "Because ascarosides were so consistently and specifically associated with nematodes, we wondered whether they could be perceived by other organisms as a 'molecular signature' of nematode threat. In particular, we were curious as to whether ascarosides could impact plant immunity. We showed that, yes, plant immune systems do respond to ascarosides, though initially it wasn't clear just what that response is."
In the team's earlier studies on nematode-plant interactions, one ascaroside in particular stood out for its ability to activate hallmarks of plant defense responses—ascaroside 18 (ascr#18). Recognition of ascr#18 granted plants a slightly heightened state of immune vigilance and increased their resistance to bacterial, viral, fungal, and nematode pathogens.
But it wasn't simply a pre-emptive immune response. As Dr. Klessig explained, "When a plant mounts a full immune response, there's a fitness cost. They shift their energy away from growth and development to focus on fighting the pathogen. With ascr#18 treatment, we didn't see that. Ascr#18 doesn't induce a full immune response but instead signals the plants to get ready, so that they can respond to pathogens more quickly and robustly. It gives the plants immune memory without the fitness cost of immune responses."
This concept is called immune priming, and is reminiscent of how vaccines prepare our immune system for rapid responses to specific pathogens. "We knew from initial investigations that exposure to ascr#18 led to increased pathogen resistance, but we didn't know the molecular mechanism behind it," explained Dr. Conrath. "Now, we see that ascr#18 primes the plant by making changes at the chromatin level. These changes establish a long-lasting state of immune memory by increasing the accessibility of defense genes to the transcriptional machinery, allowing them to be activated more rapidly when infection occurs."
Immune priming via ascr#18 is effective in a wide variety of agriculturally important crops. Notably, the team demonstrated its translatability to the field, where foliar application reduced fungal disease severity and improved yield in corn and soybean. Remarkably, simply soaking seeds in an ascr#18 solution was sufficient to prime plants for enhanced defense later in development. Unlike treatments that must be applied to plants shortly before or during pathogen attack, this seed-treatment approach could provide lasting immune benefits from the start of the growing season.
"The need for this technology is huge today," states Dr. Manohar. "We have had strategies to target plant pathogens for a long time, but pathogens adapt and develop resistance. Other products available today stimulate immune responses at the expense of growth and development. We need innovations like this, strategies that go beyond targeting the pathogen and strengthen the plant from within."
Dr. Manohar also emphasized the ease of use and affordability of ascr#18 for immune priming. "Ascr#18 is a simple compound with a very simple application process, and it can be applied to virtually any crop. It's inexpensive to produce and you need significantly less ascr#18 to treat a field than you do other commercial products. So overall it's very accessible to the average farmer."
Natural products like ascr#18 that are effective in readying plant defenses to a broad range of pathogens but do not sacrifice development or yield have incredible potential for commercial application. When plant pathogens are responsible for such staggering crop losses that threaten global food security, these products could be the key to long-term solutions and sustainability.
Written by Alyssa Kearly
About the Boyce Thompson Institute (BTI)
As an independent nonprofit research institute affiliated with Cornell University, our scientists are committed to advancing solutions for global food security, agricultural sustainability, and human health. Through groundbreaking research, transformative education, and rapid translation of discoveries into real-world applications, BTI bridges fundamental plant and molecular science with practical impact. Discovery inspired by plants. Learn more at BTIscience.org .
