A ‘Jumping Gene’ Was Caught Leaping Between Species—and It Could Rewrite the Rules of Evolution

3 min readHere’s what you’ll learn when you read this story:Self-splicing introns, found mostly in prokaryotes, are thought to potentially move between species using viruses or plasmids. A new study found evidence of a self-splicing intron in the archaea prey species of the anaerobic bacterium Candidatus Velamenicoccus archaeovorus. Introns are thought to play a role in the evolutionary process, and discovering a new pathway for this process gives scientists a better understanding of their life-changing power.The double helix structure of DNA looks remarkably stable—nucleotides and nitrogen-bases form the curvy, step-ladder-like form that appears immutable—but this couldn’t be further from the truth. Bacteria, plants, and animals (including us humans) are host to genetic parasites known as “jumping genes,” which can cut themselves free from RNA and reinsert themselves in other parts of an organism’s genome.These are known as “transposable elements,” or “transposons,” and make up nearly half of the human genome—but they aren’t the only genetic elements that move from one place to another. Introners are a kind of genetic parasite that slip into genomes and multiply. According to scientists, this may explain why genomes appear fragmented or as a series of non-coding introns followed by exons (expressed regions kept within RNA molecules). Interestingly, bacteria, archaea, and some lower eukaryotes contain self-splicing introns that use an enzyme called a “ribozyme” to excise themselves from RNA, making them independent within the cell.While it’s normal for these changes to occur within an organism or cell, it isn’t normal for these introns to “jump” to other species entirely. But a new study published in the journal Scientific Reports found evidence of one of these kinds of “jumping genes” crossing between predator-prey species.“Our study has shown that in microorganisms jumping genes can be transferred to other species via their circular RNA,” Jens Harder from the Max Planck Institute for Marine Microbiology said in a press statement. “Applications in RNA vaccines, for example, against the Covid virus and certain forms of cancer, are […] in the pipeline.”Because these genetic elements are only present in prokaryotes (for the most part), scientists analyzed a predator anaerobic bacterium known as Candidatus Velamenicoccus archaeovorus within a slow-growing, methane-producing community that breaks down limonene—a chemical compound that gives citrus peels its distinct smell.The “prey” part of this equation is a methanogenic archaea known as Methanothrix soehngenii, a favorite delicacy of Ca. Velamenicoccus archaeovorus that feasts on organisms which break down limonene. Scientists have theorized that introns might travel between species with an intermediary, such as a virus or plasmid (extrachromosomal DNA molecule), but this study found a new mechanism entirely.While studying this predator, Harder stumbled across an self-splicing intron (which typically isn’t seen outside the cell) and decided to see if introns could be found within the prey species as well. Using nuc­leic acid probes, the team captured microscopic images that detailed the presence of introns in the prey species as well. There was just one problem—the M. soehngenii specimen was already dead. Essentially, the intron tried to replicate, but its new host was already dead.“Our observations provide in vivo evidence of the mobility of intron RNA between cells of different organisms,” Harder and his colleagues wrote in the paper. “This is a prerequisite for a transposition into a foreign species, for a horizontal gene transfer.”Because these introns form a ring, they’re more resistant to degradation than typical ribonucleic acids, which break down from the ends. This allowed the intron to persist despite the cell being dead, as dead cells typically don’t retain these acids.Scientists theorize that jumping genes, including introns, might play a role in evolution—even speeding up the process entirely. Finding a new way for introns to travel among species could provide a key piece of evidence in the effort to understand the evolutionary impact of these kinds of mobile genetic elements.Darren lives in Portland, has a cat, and writes/edits about sci-fi and how our world works. You can find his previous stuff at Gizmodo and Paste if you look hard enough.