Will the water bear worm whose life ability is against the sky also be affected by the weather change?

Water bear is not a species, but a collective name of slow-moving animals, which consists of more than 1000 species. These 8-claw Michelin-like guys look simple, but their tolerance to extreme environments is amazing. Water bear insects have a wide range of habitats, and they can be found in the ocean, fresh water and even swamps. Water bear worms can only grow and reproduce in the water environment, and when the sludge dries up, they also have their own way: let themselves dehydrate and shrink, and enter a reversible "dehydrated organism" state. In the "dormant" state, water bear insects can tolerate all kinds of extreme physical environments, and scientists have always been very interested in the principle behind this.

Through genome analysis, the Japanese research team found a magic weapon for water bear insects to fight against extreme environment-a kind of "radiation-proof" protein. With it, the DNA damage caused by X-ray irradiation can be significantly reduced. Related papers were published in the journal Nature Communication on September 20th.

Water bear recovering from dehydration. Video recorder: Daishu Horikawa

Secrets in the genome

In fact, this is not the first time that scientists have tried to find the tolerance mechanism of water bears. Last year, some geneticists sequenced a freshwater water bear (Hypsibius dujardini). They claimed that a large number of foreign genes from other organisms were found in the genome of water bears, and thus put forward the hypothesis that water bears obtained environmental tolerance genes from other organisms through "horizontal gene transfer". However, scientists soon questioned that the genome data was contaminated by microorganisms and the results were unreliable.

This time, Japanese researchers chose the most tolerant species (Ramazzottius varieornatus), sequenced its genome, and studied the gene expression at different stages. In order to avoid microbial contamination during sequencing, they thoroughly disinfected the water samples with hypochlorite and antibiotics.

The sequencing results showed that there were few genes from foreign organisms (only 1.2%), which was far lower than the previously reported results. The results confirmed that the key gene of water bear insect's resistance to extreme environment came from its own evolution, not from other exogenous organisms.

What's so special about the gene of this water bear worm? Compared with other animals, it has more superoxide dismutase genes and more copies of MRE 1 1 gene (used to repair DNA double-stranded breaks). These genes can help reduce oxidative damage and repair DNA, thus playing a protective role. In addition, some genes related to environmental stress are still missing in water bears, which may also help them tide over the difficulties.

Radiation protection "shielding"

Through the study of genome and gene expression, scientists also found a unique weapon for water bears to resist radiation damage-Damage suppressor (Dsup). This protein has been expressed in large quantities since the embryonic period of the water bear worm. It can be combined with DNA and used as a "shield" against radiation damage.

In water bears, Dsup protein acts as a "shield" for DNA to resist radiation.

This protein "shield" can also protect other cells. The researchers let human cells cultured in the laboratory also express this "shielding protein". Results: Compared with the normal cells without "shielding", the cells expressing Dsup protein still maintained certain cell activity and proliferation ability after receiving X-ray radiation, and their DNA damage was reduced by 40% compared with the control group.

Knowing this protein "shield", one day human beings may also be able to improve their own or other creatures' ability to resist X-ray radiation, and may become more adaptable to the space environment, but this will not happen soon. The researchers also said that Dsup protein is not omnipotent. Although the effect is obvious, it only reduces DNA damage by about half.