New Tardigrade Study Unveils Radiation Survival Secrets

Tardigrades, eight-legged microorganisms colloquially known as "water bears," are the most radiation-tolerant animals on Earth. Now, by studying a newly identified species of tardigrade, researchers have gleaned valuable insights into the animal's ability to withstand radiation. These findings hold implications for safeguarding human health in extreme environments, such as spaceflight. Roughly 1,500 species of tardigrades have been described. These creatures can endure gamma radiation doses nearly 1,000 times higher than the lethal limit for humans. Previous studies investigating how they do this have shown that tardigrades possess robust DNA repair capabilities. They also express a tardigrade-specific protein called damage suppressor (Dsup), which, when expressed in human cells, protects DNA from radiation damage. Despite these insights, however, much remains unknown about the mechanisms underlying tardigrades' remarkable radiation resilience. Here, Lei Li and colleagues describe H. henanensis sp. nov. – a newly identified species of tardigrade. Through detailed morphological and molecular analysis, they explore the basis of the species' radiotolerance. The researchers evaluated how exposure to heavy ion radiation altered the animal's molecular profiles; they report that 285 stress-related genes were upregulated. The authors further uncovered three molecular mechanisms that contribute to radiotolerance in the organisms. First, the horizontally transferred bacterial gene DOPA dioxygenase 1 (DODA1) enhanced radiation resistance by producing betalains – pigments with potent free radical scavenging properties typically found in plants, fungi, and bacteria. Second, a tardigrade-specific protein, TDP1, facilitates the repair of DNA double-strand breaks. Lastly, the mitochondrial chaperone gene BCS1, which expanded during tardigrade evolution, is uniquely upregulated in response to radiation, shielding cells from radiation-induced mitochondrial damage. "Extreme environmental resistance of extremophiles such as tardigrades is a treasure trove of unexplored molecular mechanisms of stress resistance," write Li et al. "Functional research on these radiotolerance mechanisms… will further broaden our understanding of cellular survival under extreme conditions and may provide inspiration for promoting human health and combating disease."