original version of this story appeared in Quanta Magazine.
The world is a dangerous place for RNA molecules. Unlike DNA, which can survive for millions of years in a surprisingly stable double-stranded form, RNA is not built to last, even within the cell that created it. Unless it is protectively attached to a larger molecule, RNA can degrade within minutes. And outside the cell? Forget it. Voracious RNA-destroying enzymes are ubiquitous and secreted by all forms of life as a defense against viruses that write their genetic identity in RNA code.
There is one way for RNA to survive intact outside the cell. It’s inside a small protective bubble. For decades, researchers have noticed that cells release cell membrane bubbles called extracellular vesicles (EVs) filled with degraded RNA, proteins, and other molecules. However, these bags were thought to be little more than garbage bags that pulled out decomposed molecular junk from cells during routine cleanup.
Then, in the early 2000s, experiments led by molecular biologist Hadi Varady at the University of Gothenburg revealed that the RNA inside some EVs doesn’t look like garbage. The cocktail of RNA sequences was quite different from those found inside cells, and these sequences were intact and functional. When Valadi’s team exposed human cells to EVs from mouse cells, they saw how the human cells took up the RNA message, “read” it, and produced functional proteins that they could not otherwise make. I was shocked when I observed it.
Valadi concluded that cells specifically package RNA strands into vesicles to communicate with each other. “If you’re outside and you see it’s raining, you can say, ‘If you’re going to go out, please bring an umbrella,'” he said. In a similar way, he suggested, cells could warn neighboring cells about exposure to pathogens or harmful chemicals before they encounter danger.
Since then, improvements in sequencing technology that have allowed scientists to detect and decipher smaller and smaller RNA segments have uncovered a wealth of evidence supporting this theory. Since Valadi published his experiments, other researchers have also observed EVs filled with complex RNA combinations. These RNA sequences contain detailed information about the cell that created them and can cause specific effects in recipient cells. This discovery has led some researchers to suggest that RNA may be a molecular lingua franca that transcends traditional taxonomic boundaries, and thus can encode messages that are understandable across the tree of life. .
In 2024, new research reveals further layers to this story, showing, for example, that along with bacteria and eukaryotic cells, archaea also exchange vesicle-bound RNA, making this phenomenon one of the three It was confirmed that it is universal in all three areas. Another study showed that plants and the fungi they infect can use packets of wreaking havoc as a form of coevolutionary information warfare, expanding our understanding of cellular communication across kingdoms. Enemy cells read the RNA and build proteins that self-harm in their own cells. Molecular machines.
“I’m in awe of what RNA can do,” said Amy Buck, an RNA biologist at the University of Edinburgh, who was not involved in the new research. For her, understanding RNA as a means of communication “goes beyond understanding the sophistication and dynamic nature of RNA within cells.” Sending information across cells may be one of the primary roles of cells.
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Microbiologist Suzanne Erdmann studies viral infections. haloferax volcanoa single-celled organism that thrives in incredibly salty environments such as the Dead Sea and the Great Salt Lake. Although unicellular bacteria are known to widely exchange EVs, H. volcanii is not a bacteria. It is an archaea, a member of the third evolutionary division of life, and is characterized by cells that are structured differently than bacteria and eukaryotes like us.
Because EVs are the same size and density as the virus particles that Erdmann’s team studies at Germany’s Max Planck Institute for Marine Microbiology, she says, “they always appear when you isolate and purify a virus.” Eventually, her group became curious and decided to take a peek to see what was inside.
(Tag translation) quanta magazine
