100-million-year-old killer genes found in yeast

(ORDO NEWS) — Scientists at the Stowers Institute for Medical Research (USA) and the National Institute of Biological Sciences in Beijing have discovered a family of selfish genes that have existed for more than a hundred million years. The discovery is reported in eLife magazine.

Meiosis drivers are specific pieces of DNA that influence cell division in such a way as to promote their own transmission to offspring in more than 50 percent of cases.

In other words, these are harmful gene variants that tend to crowd out normal gene variants, affecting the very process of inheritance.

It is believed that meiotic drivers may exist for relatively short periods of evolutionary time, since the same selfish gene (or family of genes) is often found in the same species or closely related species.

In addition, it is assumed that the drivers are doomed to rapid extinction, since they negatively affect the ability of the organism to adapt and survive.

In one case, they contribute to the selection of third-party suppressor genes that suppress the activity of selfish genes.

In another case, the driver variant is fixed in the population, that is, it becomes the sole representative of the gene, after which it may disappear along with all carriers.

In a new study, scientists analyzed the evolutionary history of wtf driver genes, first discovered in the fission yeast Schizosaccharomyces pombe.

They are powerful genetic parasites, as they are not only passed on to more than half of the offspring, but also contribute to the death of reproductive cells – in the case of yeast, these are spores – which are lucky enough not to inherit the driver gene.

Homologous genes having similar nucleotide sequences and the same location on the chromosome have been identified in three other fission yeast species: S. octosporus, S. osmophilus, and S. cryophilus, which are thought to have diverged from the S. pombe lineage about 119 million years ago.

The researchers confirmed that a common ancestor of the analyzed genes existed in a common ancestor of all four yeast species.

The ability for meiotic drive is absent in the homologous genes of S. osmophilus and S. cryophilus, but the homologous gene of S. octosporus has all the features of a selfish gene.

Since it is unlikely that meiosis drivers arose independently of each other in the evolutionarily related species S. pombe, the ancestral gene was probably also a driver.

Thus, the authors proved that meiotic drive systems can be maintained during periods of evolution that are at least ten times longer than those previously thought possible.


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