Biology

RNA "evolution" breakthrough offers new clues on the origins of life

RNA "evolution" breakthrough o...
RNA molecules can replicate in a process like evolution, which may have implications for the origins of life, according to a new study
RNA molecules can replicate in a process like evolution, which may have implications for the origins of life, according to a new study
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RNA molecules can replicate in a process like evolution, which may have implications for the origins of life, according to a new study
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RNA molecules can replicate in a process like evolution, which may have implications for the origins of life, according to a new study

Researchers at the University of Tokyo have created an RNA molecule that can not just replicate, but “evolve” into a diverse range of more complex molecules. This find could plug a major gap in the puzzle of how life on Earth began.

Exactly how life arose from non-living matter is one of the most profound mysteries of science. It’s long been hypothesized that RNA acted as a kind of precursor to DNA – if these simple molecules existed in the “primordial soup” of early Earth, they could have begun self-replicating and diversified into a range of forms. As the molecules became more complex, they could eventually have given rise to cells with DNA molecules, birthing all forms of life we see today.

As neat as this explanation would be, it remained unknown whether or not RNA molecules could actually undergo this kind of evolution. So for the new study, the Tokyo researchers conducted a long-term RNA replication experiment.

The team incubated RNA replicase molecules in droplets of water encased in oil, at 37 °C (98.6 °F) for five hours at a time. Then nutrients were added, diluting the solution to one-fifth of the original concentration, and the mix was stirred before being left to incubate for another five hours. This process was repeated over 240 cycles, for a total of 1,200 hours of experiment time.

And sure enough, the RNA molecules mutated and diversified over time. The single starting “species” eventually branched into five different lineages, which would fluctuate in population before stabilizing. A network of interactions arose between the different lineages – most intriguingly, cooperation that helped them all replicate more efficiently.

“Honestly, we initially doubted that such diverse RNAs could evolve and coexist,” said Ryo Mizuuchi, corresponding author of the study. “In evolutionary biology, the ‘competitive exclusion principle’ states that more than one species cannot coexist if they are competing for the same resources. This means that the molecules must establish a way to use different resources one after another for sustained diversification. They are just molecules, so we wondered if it were possible for nonliving chemical species to spontaneously develop such innovation.”

While the experiment shows that it’s at least possible that RNA could undergo evolution and lead to complex life, that doesn’t necessarily confirm that this is how it occurred in the real world. The team plans to conduct further experiments to uncover in more detail how RNA could have paved the way towards living systems.

The research was published in the journal Nature Communications.

Source: University of Tokyo

3 comments
3 comments
aksdad
Hmmm...how did the RNA replicate? DNA and RNA are simply long chains (polymers) of repeating sequences of 4 molecules that encode genetic information much like the binary ones and zeroes on a magnetic disk or in a semiconductor memory chip. By themselves they are useless and can do nothing but sit and wait to be read. A computer program designed to read the sequence of bits can do all kinds of things including replicating them to be stored somewhere else. Likewise cellular organisms that can read the RNA or DNA can do something with them, even replicate them. But sequences of RNA or DNA in the absence of a living cell that can process the instructions encoded in them are lifeless bits of flotsam. According to the study, they used E. coli to replicate "primordial" RNA and observed over numerous generations that it diversified. Big deal. Try mixing a bunch of RNA or DNA in a vat with no E. coli or other living cells to read them then shake them, stir them, heat them, cool them, zap them with electricity, whatever, and see how many organize and begin to replicate. I'll bet it's zero.
TechGazer
Most RNA can't self-replicate, but some can. A quick google showed that it was first discovered in 2009. That research found mutations that survived too. I vaguely recall some theories about RNA using clay flakes as templates, so it's possible that a mineral substrate was involved in assembling the organic molecule that was the start of life on this planet.
Gordien
To evolve, the molecules have to want to evolve. The will to survive is a great motivator. Without the E.coli, it is difficult to see where the 'want' comes from.