Researchers identify 'dimmer switch' for plants' immune system
tags:
As sulfur becomes increasingly scarce in soils worldwide, scientists are studying how plants decide whether to invest limited resources in growth or defense.
New research points to a mechanism that helps plants reprogram their molecular machinery to budget sulfur—a critical nutrient used for both functions.
Michigan State University researchers published a study in the Proceedings of the National Academy of Sciences detailing how this adaptive allocation strategy allows plants to allocate sulfur without dropping their defenses.
A molecular "dimmer switch"—a protein called CDK8—regulates the use of sulfur in plants' defenses, allowing them to turn production of sulfur-containing defense compounds up or down, rather than strictly on or off.
"To stay healthy and resilient, plants deploy these costly chemical defense strategies," said coauthor Hideki Takahashi, an associate professor of biochemistry and molecular biology.
This mechanism enables plants to switch to low-sulfur alternatives when possible and conserve sulfur for uses where it's irreplaceable.
"This finding provides new insight into how plants balance immunity with nutrient availability and highlights a broader principle: Biological systems actively allocate limited resources among competing needs," said Gregg Howe, a University Distinguished Professor in the MSU–DOE Plant Research Laboratory and the Department of Biochemistry & Molecular Biology.
Stretching sulfur in short supply
CDK8 helps boost the activity of hormone-triggered genes responsible for plant defenses, helping plants produce a robust arsenal of defenses. In plants grown in sulfur-deficient soils, CDK8 shifted plants' assembly line toward lower-sulfur alternatives. Production of defense compounds containing only one sulfur atom increased nearly eightfold, while production of those containing two or three times as much sulfur was reduced. It's a cost-conscious strategy, the authors explain.
"There is no alternative to staples like amino acids—these irreplaceable biological building blocks require sulfur," Takahashi said.
When sulfur is limited, plants may become malnourished, resulting in slower growth and smaller size. But CDK8 can lessen these impacts by switching to defense strategies that free up sulfur for growth.
A subset of plants modified to have inactive CDK8—effectively disconnecting the dimmer switch—were found to have lower levels of sulfur-based defense compounds and diminished resistance to pests and diseases. This demonstrates not only the role of CDK8 in promoting the production of defense compounds but also that mutants without CDK8 are unable to properly reprogram their defense mechanisms when there's a decrease in available sulfur, Howe explained.
Why are scientists studying sulfur?
How plants allocate sulfur is a time-sensitive question, as stores of plant-available sulfur—and the deposition that has historically replenished reserves—are in steep decline worldwide. In the United States, plant-available sulfur in soil has declined by up to 86% in the past two decades.
These findings provide scientists with clues about how more efficient, "budget-conscious" crops might be designed. Such plants could be engineered to be more resistant to disease and less vulnerable when nutrient levels dip.
The next step, Takahashi suggests, is to study how plants sense the nutrients around them. This is another steppingstone to understanding how plants use environmental cues to make decisions.
Publication details
Qiang Guo et al, CDK8 coordinates jasmonate-induced immunity with sulfur-responsive defense in Arabidopsis, Proceedings of the National Academy of Sciences (2026). DOI: 10.1073/pnas.2609022123
Who's behind this story?
Swati Mestri holds a bachelor's degree in Electronics Engineering and has worked as a content editor since 2019. She has experience editing research documents across technology, health care, and materials science, and has a particular interest in technology and space. Full profile →
Master's in physics with research experience. Long-time science news enthusiast. Plays key role in Science X's editorial success. Full profile →
Citation: Researchers identify 'dimmer switch' for plants' immune system (2026, July 17) retrieved 17 July 2026 from https://phys.org/news/2026-07-dimmer-immune.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.