New species of tardigrade reveals secrets of radiation resistance

A newly described species of tardigrade gives scientists insight into what makes these tiny, eight-legged creatures so resistant to radiation.

Tardigradesalso known as water bears, have long fascinated scientists with their ability to withstand extreme conditions, including radiation levels nearly 1,000 times the lethal dose to humans. About one and a half thousand species of tardigrades are known, but only a few of them are well studied.

The earliest description of these animals was made by the German pastor Johann August Ephraim Goeze in 1773. In it he compared them to bears, calling kleiner Wasserbär (with him. – “little water bear”) – approx. lane

Now scientists have sequenced the genome of a species new to science and have identified some of the molecular mechanisms that provide tardigrades with their extraordinary vitality. Study, published in the journal Science on October 24, identified thousands of genes in tardigrades that are activated when exposed to radiation. These processes point to a complex defense system that involves protecting DNA from damage caused by radiation and repairing any breaks that occur.

The authors hope their discovery could be used to protect astronauts from radiation during space flight, clean up nuclear waste, or treat cancer more effectively.

“This discovery could help improve the resistance of human cells to radiation and benefit patients undergoing radiation therapy,” said study co-author Linqiang Zhang, a molecular and cellular biologist at the Beijing Biomics Institute.

Defense genes

About six years ago, Zhang and his colleagues went to Mount Funiu in China's Henan province to collect moss samples. Returning to the laboratory and examining them under a microscope, they discovered a previously undescribed species of tardigrades, which they gave the name Hypsibius henanensis. Genome sequencing has shown that this species has 14,701 genes, 30% of which are unique to tardigrades.

When researchers exposed H. henanensis to doses of 200 and 2000 radiation gray– far beyond what is normal in humans – they found that 2,801 genes involved in DNA repair, cell division and immune responses became active.

“It’s similar to how factories are converted to produce ammunition in wartime. It's almost the same level of reconfiguration gene expression ” says Bob Goldstein, a cell biologist at the University of North Carolina at Chapel Hill who has been studying tardigrades for 25 years. “What fascinates us is how an organism can change the expression of genes to the point where they produce so much transcriptsfor certain genes.”

One of the genes, called TRID1, encodes a protein that helps repair DNA double-strand breaks by recruiting specialized proteins to the site of damage. “This is new [ген]which, to my knowledge, no one has studied,” says Goldstein.

The researchers also suggest that 0.5-3.1% of tardigrade genes were acquired from other organisms through a process known as horizontal gene transfer. A gene called DODA1, which appears to have come from bacteria, allows tardigrades to produce four types of antioxidant pigments called betalains . These pigments can absorb some of the harmful chemically active substances that are formed in cells under the influence of radiation and which account for 60-70% of the damaging effects of radiation.

The authors treated human cells with one of the tardigrade betalains and found that they tolerated radiation much better than untreated cells.

No expiration date

Studying the molecular mechanisms that allow tardigrades to survive other harsh conditions, such as extreme temperatures, air deprivation, dehydration and starvation, could have broad applications. For example, it could improve the shelf life of highly perishable substances such as vaccines. “All your medications have an expiration date, but tardigrades don't,” says Goldstein.

Comparing these mechanisms across different tardigrade species is an important part of the study, adds Nadja Møbjerg, an animal physiologist at the University of Copenhagen. “We still lack knowledge about the different species of tardigrades,” she says.

These animals have “a source of protective substances that will likely continue to be secreted, and this will be useful and interesting to study,” Goldstein says. “We want to understand how they work and what their potential is.”

Original news was publishedin the journal Nature on October 24, 2024.