In a groundbreaking study, Princeton engineers found that specific soil bacteria produce an enzyme capable of balancing plant growth and immunity, opening new avenues for agricultural innovation.
In a remarkable breakthrough that promises to revolutionize agricultural practices, researchers at Princeton University have discovered that certain soil bacteria produce an enzyme capable of balancing plant growth and immune response. This finding, detailed in a report published in the journal Cell Reports, offers a novel perspective on the intricate relationship between plants and their microbial companions.
The study, spearheaded by a multidisciplinary team of Princeton engineers and biologists, revealed that the enzyme produced by harmless or beneficial soil bacteria can modulate a plant’s immune activity. This modulation allows plants to divert more energy towards root growth, which could significantly impact agricultural productivity.
“This is trying to get at a really big biological question where there are not good answers — about how microbiomes interface with host immune systems,” senior author Jonathan Conway, an assistant professor of chemical and biological engineering, said in a news release. “It’s a small step in the direction of trying to understand how microbes live on hosts — either plants or humans or other animals — all the time and don’t activate our immune responses constantly.”
The research focused on Arabidopsis thaliana, a small flowering plant commonly used in scientific studies. The Princeton team genetically engineered Arabidopsis seedlings to have a heightened immune response to a bacterial protein called flagellin, which is known to trigger immunity in hosts ranging from plants to humans. When exposed to flagellin, these seedlings typically exhibit stunted root growth as their resources are siphoned away from development and redirected towards defense.
However, when the team introduced 165 different bacterial species isolated from the roots of soil-grown Arabidopsis, they found that 41% of these isolates could suppress the seedling’s stunted growth by reducing immune activity. Notably, one bacterium, Dyella japonica, emerged as a prominent facilitator of root growth.
The research then identified an enzyme secreted by D. japonica – a subtilase – that appears to degrade flagellin, thereby mitigating the immune response and allowing the plants to grow more effectively. Utilizing genetic and biochemical methods, the team confirmed that this subtilase enzyme could indeed break down the immune-triggering segment of flagellin.
Samuel Eastman, a co-first author and postdoctoral research associate in Conway’s lab, noted that collaboration was pivotal in advancing the study. Difficulty in purifying the enzyme was resolved after a conference meeting led to assistance from Todd Naumann, a chemist with the USDA’s Agricultural Research Service.
“Now we can do chemistry with it, and we can actually look at this in vitro,” Eastman said in the news release. “We’re able to achieve a level of investigation into this protein that wouldn’t have been possible without that collaboration.”
The findings open potential pathways to enhance agricultural practices by leveraging natural soil bacteria to improve plant health and yield. However, the researchers caution that further study is essential to fully understand the implications, especially since reduced immune responses could make plants more susceptible to diseases.
“We don’t want to compromise the immune system, but we also want plants to save that immune response for when it matters,” Eastman added. “We want them to keep calm and keep growing.”
This multifaceted study not only underscores the symbiotic relationship between plants and their microbiomes but also paves the way for innovative strategies to cultivate more resilient crops, balancing growth and defense naturally.
The study, co-authored by Eastman, Conway and their collaborators, including postdoctoral research associates Ting Jiang and 2024 Princeton graduate Kaeli Ficco, highlights the potential of soil microbiota in agricultural advancement. Ficco, who is now pursuing her doctorate at Cornell University, played a crucial role in engineering mutant bacterial strains for the study.
“I really liked how discovery-based the project was,” said Ficco. “That definitely influenced my trajectory after Princeton.”
Such pioneering research exemplifies the potential of scientific inquiry to uncover solutions that enhance sustainability and productivity across ecosystems, providing hope for a future where plants and their microbial allies work in harmony for mutual benefit.