Genome invaders Shellder and Spoink: man-made double-trouble

To date, there has been very little evidence of the horizontal transfer of genetic material in eukaryotes - i.e. organisms whose cells have a nucleus - over short evolutionary periods. In a recently published Austrian-US study led by the University of Veterinary Medicine, Vienna, a team of scientists has now investigated transposable elements in fruit flies. They were able to prove that the two retrotransposons Shellder and Spoink have entered the genomes of several species of the melanogaster subgroup within the last 50 years.

Poto: fotolia

Retrotransposons are mobile (“transposable”) elements that move around the host genome by converting their transcribed RNA into DNA through reverse transcription. They got their name because of their structural similarity to retroviruses.

According to the researchers, Spoink spread into Drosophila melanogaster (D. melanogaster) through horizontal transfer in the 1980s, while both Shellder and Spoink invaded D. simulans in the 1990s. Possibly following hybridization, D. simulans infected the endemic island species D. mauritiana (Mauritius) and D. sechellia (Seychelles) with both transposable elements (TE) after 1995. Around the same time, Shellder also infected D. teissieri, a species that only occurs in sub-Saharan Africa.

Caused by humans: American Drosophila species identified as vectors

The scientists found that Shellder and Spoink probably originate from American Drosophila species from the willistoni, cardini and repleta groups. “The cascade of TE invasions we described could therefore only have become possible after D. melanogaster and D. simulans expanded their range to the American continent around 200 years ago, most likely aided by human activity,” explain Almorò Scarpa and Riccardo Pianezza, the first authors of the study.

Humans influence genome activities of other species

Robert Kofler, project leader of the study, also emphasizes the human influence on evolution as extending beyond the immediate study results: “Our work shows that cascades of TE invasions, likely triggered by human mediated range expansion, could have an impact on the genomic and phenotypic evolution of geographically dispersed species.”

Following this scientific insight, TE could invade many species within just a few decades, including endemic island species whose range is very far from the origin of TE.

Humans have long been changing evolution - and favoring the mobility of infectious agents

Human activities have long influenced the evolutionary path of various species, particularly through the dispersal of organisms across continents and ecosystems. Climate change is further disrupting natural habitats, causing many species to expand their range or move poleward in search of more favorable conditions. This new mobility also applies to infectious agents - for example, pathogens from cultivated plants can spread worldwide, bringing them into contact with many new local species. The loss of habitats and increasing contact between humans and wild animals also creates new opportunities for the spread of diseases.

Risky development perhaps also for humans

Intragenomic invaders, which include transposable elements (TEs), may not be exempt from this dynamic, according to the researchers. “If the distribution of species changes and humans transport organisms around the planet, they could also come into contact with new genomic invaders such as TEs,” explain Scarpa and Pianezza.

The article „Double trouble: two retrotransposons triggered a cascade of invasions in Drosophila species within the last 50 years“ by Almorò Scarpa, Riccardo Pianezza, Hannah R. Gellert, Anna Haider, Bernard Y. Kim, Eric C. Lai, Robert Kofler and Sarah Signor was published in „Nature Communications“.

Scientific article

Scientific contact:
Priv.-Doz. Dr. Robert Kofler
Centre of Biological Sciences
University of Veterinary Medicine Vienna (Vetmeduni)
Robert.Kofler@vetmeduni.ac.at

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