News

Molecular sensor enables water bear hardiness by triggering dormancy

Free radicals sensor triggers tardigrades to enter a dehydrated tun state to withstand extreme stress
Patricia Waldron
By Patricia Waldron
April 6, 2024

Tardigrades – hardy, microscopic animals commonly known as “water bears” – use a molecular sensor that detects harmful conditions in their environment, telling them when to go dormant and when to resume normal life. A team led by Derrick R. J. Kolling of Marshall University and Leslie M. Hicks of the University of North Carolina at Chapel Hill report these findings in a new study published January 17 in the open-access journal PLoS ONE.

SMYTHERS ET AL., 2024, PLOS ONE, CC-BY 4.0
A tardigrade, observed using a confocal fluorescent microscope, was overexposed to 5-MF, a cysteine selective fluorescent probe, that allows for visualization of its internal organs.

Water bears are famous for their ability to withstand extreme conditions, and can survive freezing, radiation, and environments without oxygen or water. They persist by going dormant and entering a tun state, in which their bodies become dehydrated, their eight legs retract and their metabolism slows to almost undetectable levels. Previously, little was known about what signals water bears to enter and leave this state.

In the new study, researchers exposed water bears to freezing temperatures or high levels of hydrogen peroxide, salt or sugar to trigger dormancy. In response to these harmful conditions, the animals’ cells produced damaging oxygen free radicals. The researchers found that water bears use a molecular sensor—based on the amino acid cysteine—which signals the animals to enter the tun state when it is oxidized by oxygen free radicals. Once conditions improve and the free radicals disappear, the sensor is no longer oxidized, and the water bears emerge from dormancy. When the researchers applied chemicals that block cysteine, the water bears could not detect the free radicals and failed to go dormant.

Altogether, the new results indicate that cysteine is a key sensor for turning dormancy on and off in response to multiple stressors, including freezing temperatures, toxins and concentrated levels of salt or other compounds in the environment. The findings suggest that cysteine oxidation is a vital regulatory mechanism that contributes to water bears’ remarkable hardiness and helps them survive in ever-changing environments.

"Our work reveals that tardigrade survival to stress conditions is dependent on reversible cysteine oxidation, through which reactive oxygen species serve as a sensor to enable tardigrades to respond to external changes," the authors stated.

Enjoy reading ASBMB Today?

Become a member to receive the print edition four times a year and the digital edition monthly.

Learn more
Patricia Waldron
Patricia Waldron

Patricia Waldron is a science writer in upstate New York. She wrote this article on behalf of PLOS.

Get the latest from ASBMB Today

Enter your email address, and we’ll send you a weekly email with recent articles, interviews and more.

Latest in Science

Science highlights or most popular articles

What’s in a diagnosis?
Essay

What’s in a diagnosis?

Sept. 4, 2025

When Jessica Foglio’s son Ben was first diagnosed with cerebral palsy, the label didn’t feel right. Whole exome sequencing revealed a rare disorder called Salla disease. Now Jessica is building community and driving research for answers.

Peer through a window to the future of science
Annual Meeting

Peer through a window to the future of science

Sept. 3, 2025

Aaron Hoskins of the University of Wisconsin–Madison and Sandra Gabelli of Merck, co-chairs of the 2026 ASBMB annual meeting, to be held March 7–10, explain how this gathering will inspire new ideas and drive progress in molecular life sciences.

Glow-based assay sheds light on disease-causing mutations
Journal News

Glow-based assay sheds light on disease-causing mutations

Sept. 2, 2025

University of Michigan researchers create a way to screen protein structure changes caused by mutations that may lead to new rare disease therapeutics.

How signals shape DNA via gene regulation
Journal News

How signals shape DNA via gene regulation

Aug. 19, 2025

A new chromatin isolation technique reveals how signaling pathways reshape DNA-bound proteins, offering insight into potential targets for precision therapies. Read more about this recent MCP paper.

A game changer in cancer kinase target profiling
Journal News

A game changer in cancer kinase target profiling

Aug. 19, 2025

A new phosphonate-tagging method improves kinase inhibitor profiling, revealing off-target effects and paving the way for safer, more precise cancer therapies tailored to individual patients. Read more about this recent MCP paper.

How scientists identified a new neuromuscular disease
Feature

How scientists identified a new neuromuscular disease

Aug. 14, 2025

NIH researchers discover Morimoto–Ryu–Malicdan syndrome, after finding shared symptoms and RFC4 gene variants in nine patients, offering hope for faster diagnosis and future treatments.