Last updated July 12, 2018 at 12:39 pm
And they’ve been a big driver of evolution.
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Cross-species gene transfers have occurred frequently throughout evolution, even between plants and animals, according to Australian researchers.
In fact, the widespread transfer of genes has been an important driver of evolution, radically changing the genomes of today’s mammals, they say.
A team from the University of Adelaide, working in collaboration with the South Australian Museum, carried out what they say was the world’s largest study of so-called “jumping genes”, tracing two of them across 759 species of plants, animals and fungi.
Properly called retrotransposons, jumping genes are small pieces of DNA that can copy and paste themselves around genomes and in genomes of other species, according to project leader Professor David Adelson, Director of the University’s Bioinformatics Hub.
“How they do this is not yet known although insects like ticks or mosquitoes or possibly viruses may be involved – it’s still a big puzzle,” he said.
Horizontal transfer
“This process is called horizontal transfer, differing from the normal parent-offspring transfer, and it’s had an enormous impact on mammalian evolution.”
For example, 25% of the genome of cows and sheep is derived from jumping genes.
“Think of a jumping gene as a parasite,” Adelson said. “What’s in the DNA is not so important: it’s the fact that they introduce themselves into other genomes and cause disruption of genes and how they are regulated.”
Both of the jumping genes the Adelaide team traced – L1 and BovB – entered mammals as foreign DNA. This is the first time anyone has shown that L1, which is important in humans, has jumped between species.
“L1 elements were thought to be inherited only from parent to offspring,” said lead author Dr Atma Ivancevic, a postdoctoral researcher in the University’s Medical School. “Most studies have only looked at a handful of species and found no evidence of transfer. We looked at as many species as we could.”
Evolution of diseases
L1 elements in humans have been associated with cancer and neurological disorders. The researchers say that understanding the inheritance of this element is important for understanding the evolution of diseases.
They found L1s are abundant in plants and animals but only appear sporadically in fungi. The most surprising result was the lack of L1s in the Australian monotremes – the platypus and echidna – showing that the gene entered the mammalian evolutionary pathway after the divergence from monotremes.
“We think the entry of L1s into the mammalian genome was a key driver of the rapid evolution of mammals over the past 100 million years,” Adelson said.
BovB is a much younger than L1. It was first discovered in cows, but has since been shown to jump between a wide array of animals including reptiles, elephants and marsupials. It has transferred at least twice between frogs and bats, and new potential vector species include bed bugs, leeches and locusts.
The paper published in Genome Biology.
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