An article published in the journal “Genome Biology” describes a research on some transposons, commonly called jumping genes because they can move within the DNA of an organism, typically leaving copies of themselves in the original location. A team of researchers looked for traces of two transposons, identified as L1 and BovB, in 759 species of plants, animals and fungi. Their theory is that they have become parts of mammalian DNA through a horizontal gene transfer, which means acquiring them from another species.
The L1 (LINE-1) transposon is associated with cancers and neurological disorders so its study is also important for medical research because of the possibility of providing new information on the evolution of those diseases. It’s common in plants and animals while it’s rare in fungi. A surprising result is that it’s missing in platypuses and echidnas, a fact that suggests that it became part of mammals’ DNA after the separation with the order of monotremes those species belong to.
Dr. Atma Ivancevic of the University of Adelaide, among the authors of the research, pointed out that most of the studies examined only a limited amount of species, finding no evidence of the L1 transposon transfer. Instead, her team examined as many species as possible.
The BovB (Bovine-B) jumping gene seems much younger than L1. To be precise, it’s a retrotransposon, meaning a jumping gene that’s still made of a piece of DNA but is multiplied not directly but through RNA intermediation.
Discovered for the first time in cows, it was subsequently identified in other species including reptiles, elephants and marsupials. This new research also discovered it in frogs and bats with transfers between the two groups. Possible vectors for those transfers may have been ticks and other parasites such as leeches and locusts.
The image (Courtesy University of Adelaide. All Rights Reserved) shows a graphical representation of how the BovB retrotransposon appeared in species that are very diverse in the evolutionary tree. It shows how a jumping gene can end up no longer in a different location in the original species’ DNA but in another species through horizontal gene transfer.
According to the researchers, the BovB retrotransposon spread more than previous studies recognized. This makes it even more important to understand the mechanisms of horizontal gene transfer, also considering its influence on the evolution of species that receive new genes.
Professor David Adelson of the University of Adelaide, who led this research, thinks his team just started scratching the surface of horizontal gene transfers. He pointed out that there are many other species to investigate and other types of jumping genes and his team also intends to study species of insects and the possibility that aquatic species can be carriers of horizontal gene transfers as well. It’s a new frontier of genetic investigations on mutations and all that follows.