In the photo: Dissostichus mawsoni - one of the largest representatives of the Nototheniaceae, can weigh up to 90 kilograms (photo by Chris Cheng and Paul Cziko).
How do Antarctic fish manage not only to exist, but also to live peacefully at temperatures close to the freezing point of water? Curious scientists have been looking for the answer to this tricky question for many years - such a "non-freeze" would be useful to mankind. Now American researchers decided to look at the root, namely, to study the functions and genes of biological antifreeze. And the new work led to a valuable discovery
Scientists from the University of Illinois undertook to examine the genome of the Antarctic toothfish (Dissostichus mawsoni) to find out what determines its fantastic endurance.
Fish of the suborder Notothenioidei inhabit the icy waters of the Southern Ocean and account for almost 90% of the fish biomass of this region. It is for this reason that geneticists chose them as test subjects. The temperature of the local waters is such that the entire body of the underwater inhabitants should have turned into ice. However, this does not happen. Why?
A careful study of the unusual abilities of the Nototenians essentially began in the fifties of the last century. In the 1960s, Professor Arthur DeVries of the University of Illinois first isolated and described "antifreeze proteins" that bind ice crystals in fish blood, preventing it from freezing. The organism of the inhabitants of the deep sea produces them itself.
There are eight families in the suborder Notothenioidei, five of them live in Antarctica, living quietly at low temperatures (-2–4 ° C) and high oxygen content (which dissolves better in cold water and transforms into highly reactive forms harmful to body tissues).
A group of geneticists led by Devris' wife Chi-Hing "Christina" Cheng set out to figure out the genetic basis for extreme endurance.
“This work was the first full-scale study of all the biological functions of fish living in incredibly cold water from birth to death,” says Cheng.
To begin with, the scientists took close control of a characteristic representative of the nontotenium - Dissostichus mawsoni. Christina and her colleagues wanted to find out which genes are most commonly expressed in the Arctic toothfish. To do this, they took four tissue samples: from the brain, ovaries, liver and kidney (the main hematopoietic organ of fish)
Promotional video:
Note, two years ago, scientists found that the liver almost does not produce the proteins necessary for adaptation. The stomach and exocrine pancreas work much more for the good of the fish.
At first, geneticists decided that Antarctic fish would have highly efficient expression of all genes that enable them to survive at low temperatures and high oxygen levels. Although the option was also considered when specific tissues produce large amounts of certain proteins.
“We found that in the vast majority of cases, a specific group of genes are at work,” Cheng says. "Every tissue expresses all possible genes, but that very small group of cytoprotective genes is expressed in large numbers in all tissues."
Next, scientists compared the expression of genes of D. mawsoni and fish unrelated to it, living in the warmer waters of the World Ocean, and found that most of the genes needed by Antarctic fish almost do not manifest themselves in other species.
Among the sequences responsible for the production of certain proteins in large quantities (upregulated genes), many genes have been found that encode proteins that are responsible for the body's response to negative environmental influences. Scientists have counted as many as 177 families.
In particular, a variety of chaperones (proteins whose main function is to restore the correct tertiary structure of damaged proteins) have been found, and especially "heat shock proteins" that protect cells from extreme temperatures. Also present were ubiquitins, proteins that support cell health and mark other proteins before degradation.
In addition, in the genome of Antarctic toothfish, these proteins are found from 3 to 300 times more often than in its warm-water "counterparts", which also increases the resistance of the fish organism to extreme conditions.
At the moment, scientists are studying the effect of climate change (increasing water temperature) on Antarctic fish species. They have to find out whether D. mawsoni can adapt to new conditions. After all, if Antarctic toothfish become extinct, all food chains of the Southern Ocean will suffer.
Read more about the study in the university press release, in the article by the authors of the discovery, published in PNAS. The University of Illinois has also prepared this slide show for informational purposes.
It is, of course, too early to talk about the practical application of the data obtained for the benefit of humans. This research is more fundamental than applied. However, whether scientists after years, with the help of new discoveries, will be able to create some kind of special antifreeze for mechanisms and products, or (if you really dream about it), to improve the ability to survive at low temperatures of a person himself - no one knows.