A new genome analysis of tardigrades has opened scientists newthe secrets of the world's most enduring animal, while casting doubt on the conclusions made in earlier studies. By comparing genes taken from two species of tardigrades, scientists determined how these animals can be associated with other species of living creatures and due to which genes these crumbs are able to survive as a result of complete dehydration.
International group of researchers fromUniversities of Edinburgh (Scotland) and Keio (Japan) sequenced genes of the species Ramazzottius varieornatus and Hypsibius dujardini tardigrades and compared them with the genes of other animals that are most similar to them.
Tardigrades, which are also called "waterat first glance, one can hardly be called the most hardy creature on the planet with their size just exceeding a millimeter in length. But do not let their small size mislead you. Recently, scientists have found that tardigrades are still "able to dance on your grave" when the real apocalypse sets in, which will destroy all life on the planet. But not them.
Such survivability is due to severalfeatures possessed by tardigrades. They are able to survive at temperatures ranging from 150 degrees Celsius and almost to absolute zero, starve for a decade. Even with complete dehydration (complete absence of water) in their body, although they dry out, they can return to life without problems as soon as environmental conditions become more suitable.
An earlier study by anotherA team of scientists found that for the ability to withstand complete dehydration, Tardigrades owe a special protein, the so-called “bioglass,” which keeps the animal’s cell structure intact until the external environment becomes wet again. As part of a new study, scientists decided to find out which gene is responsible for such a complex process. To do this, they carried out the dehydration and hydration of two species of tardigrades.
As expected, a significant portionexpressed genes was involved in the “repair” of DNA, a process that starts when, for example, a tardigrades receive a powerful dose of radiation. Other genes, in turn, began to protect DNA chains from oxidation. Comparison of the complete genome also made it possible to answer the question that tormented biologists for a long time - where is the place of these very strange creatures on the genealogical tree?
Tardigrades belong to their owntaxonomic group Tardigrada. On the one hand, their segmented bodies make them look like tiny insects, so their branch can be located closer to the crab, spiders and beetles that make up the type of arthropod. They have four pairs of plump and short legs with a branched claw, which in turn can create a very distant kinship with onychophores, a type of invertebrate. In earlier studies with genetic sampling, links were established between tardigrades and roundworms, or nematodes.
Counting the so-called HOX genes involved inestablishing the sequence of body segments in all animals, only confirmed the conclusions of these early studies, showing that tardigrades have five HOX genes, like the same nematodes. Although this evidence cannot be called convincing in favor of a direct link between the two groups, the coincidence is very remarkable, especially when you consider that most other animal species have 10 such genes. Probably, to find out all the genetic features of tardigrades, more than one such study will have to be carried out.
A couple of years ago, scientists found that 17.5percent of the genus tardigrades (which is about 6,000 genes) were obtained by them from other species. Most of them were bacteria and other microorganisms. Despite the fact that we also have several genes obtained as a result of the so-called horizontal gene transfer, this is just a huge proportion of foreign genes for the body.
According to a new study, we can withcertainty that tardigrades have a "Frankenstein" genome. However, scientists were not able to detect signs of bacterial DNA, which suggests that the results of previous studies could be erroneous.
“I am very impressed with these tiny and prettycute animals for two decades. I am glad that we were able to get a true picture of their genome, and now we can begin work that will allow us to understand these mysterious living creatures, ”says researcher Mark Blaxter from the University of Edinburgh.
Finding out all the details on how tardigradesable to repair their DNA and protect their cells from extreme temperatures and radiation, may lead to the discovery of new technologies of regenerative medicine, scientists say.
“This is just the beginning. Thanks to a more accurate understanding of their DNA, we can now find out how tardigrades resist extreme conditions and environments, and, possibly, use their special proteins in the biotechnology and medical fields in the future, ”sums up Blackster.