Why do organisms fight for survival

How "selfish" genes fight for survival

Selfish genes - in English "selfish genes" - have been an issue in biology for decades. Like parasites, they are primarily geared towards benefiting and their own reproduction and often do not bring their host any advantages.

Since 2019, the scientist Alejandro Burga has headed a research group in Vienna on an extreme sub-category of this DNA: the so-called toxin-antidote elements. These are two genes that are responsible for the production of a poison and its antidote, so to speak. Only those individuals who inherit the two parts survive. The genes make themselves vital and therefore keep spreading.

Burga has only found his current hobbyhorse in the past few years. The big questions of biology preoccupied the 35-year-old from an early age, and when the human genome was deciphered in 2003, his career was clear for him. Growing up in the Peruvian capital Lima, one thing was clear to the young Alejandro Raúl Burga Ramos: "I knew that sooner or later I would have to find a way outside of Peru to do science."

Today the situation may be a little better, but in his youth he feared that he would not be able to make a living as a researcher. Government research funding is low and the education system is considered out of date. He moved to Santiago de Chile to study biochemistry and to Barcelona for his doctorate.

From cormorant to roundworm

During his postdoc at the University of California, Los Angeles (UCLA), Burga researched which genes were essential for the evolution of the Galapagos cormorant. This bird, unlike any other member of the cormorant family, cannot fly. The same genes are responsible for its small wings that cause malformations of the extremities in other animals - including humans.

Two years ago, Burga accepted a position as group leader at the Vienna Institute for Molecular Biotechnology (IMBA) of the Austrian Academy of Sciences. Funded by the renowned Starting Grant from the European Research Council (ERC), the molecular biologist at IMBA works with self-interested genes. The model organism of his choice is usually the C. elegans worm, in which Burga has already been able to detect toxin-antidote elements.

Struggle for dominance

An example of how they work: a male worm has a toxin-antidote pair in its own DNA. As a result, it produces poisonous proteins and passes them on to all of its sperm cells. He himself is protected by the antidote. But if his offspring do not inherit the toxin-antidote genes, they cannot produce an antidote and are not viable. After all, this can affect 25 percent of the offspring.

Selfish genes fight for their own survival - and for dominance in a population. In order to implement this in the best possible way, they develop new functions, such as in this case poison and antidote. This is why Burga says, "The conflicts between these self-serving elements in DNA can be a source of innovation. It can be compared to the space competition between the United States and the Soviet Union. During the Cold War, the great powers did not fight for the first Space in space and on the moon because the idea of ​​it was so beautiful. It was about being in control of that area - a struggle for dominance. A by-product of that race was that space technology was being developed. Now we all benefit from that there are satellites. "

Biological barriers

Burga and his colleagues suspect that selfish elements could also influence the emergence of new species. In order for one species to be differentiated from another, biological barriers must arise - for example a reproductive system that is no longer compatible with certain individuals.

"As far as we know, there are only a handful of genes that play a role in the formation of such obstacles. So I wouldn't be surprised if selfish elements also contributed." The emergence of a new species could be an unplanned consequence of selfish DNA: "Species formation as a by-product of a conflict between genes that want to survive - I find this thought fascinating."

There is still little research into toxin-antidote pairs. Burga was a co-discoverer of an antidote gene that was previously thought to be a completely different gene. Other DNA segments that were previously held responsible for the correct development of organs could also be hidden antidote genes. This means that egotistical elements may be more common than expected.

And: two different egoists can also come into conflict with each other. If a large part of the offspring dies because either one or the other antidote is missing, this can cause the species to separate. "In this case, two populations with different selfish elements would be better off not mixing," says Burga. So a new species could emerge.

From Medea to Medaka

In order to better understand the clever genes, the researcher is working with structural biologists to study the gene products - that is, the poisonous proteins and their counterparts. In doing so, they want to learn how the mechanism of action works.

In the next research steps, he wants to use the fish species Medaka (Japanese rice fish) to find out whether this self-serving DNA also occurs in vertebrates. So far, it has been detected in flour beetles, for example, and referred to as the Medea element: Because the poison is passed on here through the mother's egg cells, the gene is named like the figure in Greek mythology who killed her children.

But plants, fungi and bacteria also have such genes. Therefore, Burga asks: "Why shouldn't they occur in vertebrates? And if they do not occur here: What makes us so special?" (Julia Sica, February 8th, 2021)