Scientists have discovered how beneficial soil bacteria help plants maintain a critical balance between growth and immune defense. The findings, published simultaneously in Science and Cell Reports, reveal a sophisticated molecular mechanism that allows plants to “keep calm and keep growing” while maintaining effective disease protection.
The research teams, working independently at Rice University and Princeton University, found that certain bacteria living around plant roots produce specialized enzymes that can modulate plant immune responses. This discovery helps explain how plants manage to grow robustly while maintaining defenses against pathogens.
“Imagine tiny processors inside cells made of proteins that can ‘decide’ how to respond to specific signals like inflammation, tumor growth markers or blood sugar levels,” said Xiaoyu Yang, lead author of the Science paper and a graduate student at Rice University. “This work brings us a whole lot closer to being able to build ‘smart cells’ that can detect signs of disease and immediately release customizable treatments in response.”
The key to this balance lies in an enzyme called immunosuppressive subtilase A (IssA), which the bacteria secrete into their environment. This enzyme acts like molecular scissors, precisely cutting up warning signals that would otherwise trigger the plant’s immune response. In nature, this helps prevent the plant from overreacting to harmless bacteria while still maintaining the ability to fight off genuine threats.
In laboratory experiments, the researchers found that 41% of tested root bacteria could help plants maintain better growth when their immune systems were artificially activated. The bacteria accomplished this without compromising the plants’ ability to defend against actual pathogens.
“This opens up the signaling circuit design space dramatically,” said Caleb Bashor, an assistant professor at Rice University and corresponding author on the Science study. “It turns out, phosphorylation cycles are not just interconnected but interconnectable — this is something that we were not sure could be done with this level of sophistication before.”
The discovery has significant implications for agriculture, potentially leading to new ways to promote plant growth while maintaining natural disease resistance. Caroline Ajo-Franklin, director of the Rice Synthetic Biology Institute, put the findings in perspective: “If in the last 20 years synthetic biologists have learned how to manipulate the way bacteria gradually respond to environmental cues, the Bashor lab’s work vaults us forward to a new frontier — controlling mammalian cells’ immediate response to change.”
The work represents a collaboration between multiple institutions, including Rice University, Princeton University, and the USDA’s Agricultural Research Service. The research was supported by several organizations, including the National Institutes of Health and the Office of Naval Research.
As researchers continue to explore this mechanism, they’re particularly interested in understanding whether these bacterial enzymes could be harnessed to improve crop yields without increasing vulnerability to disease. The challenge lies in finding the right balance – helping plants “keep calm and keep growing” while maintaining their ability to defend against real threats.