Tiny strand of RNA provides new insights into the origins of life

Anyone that knows me, or has read any of this blog, knows that the origins of life on Earth, and the subsequent impacts for the potential for the origins of life on other planets, is somewhat of my Roman Empire. So naturally, when I came across an article on this study from the MRC Laboratory of Molecular Biology in Cambridge I was intrigued to know more. The paper, "A small polymerase ribozyme that can synthesise itself and its complimentary strand (Gianni et al., 2026)", was published back in February in the journal Science. What caught my eye about the article's title is the self-synthesis part, as being able to make a new version of yourself is the root of evolution. The title essentially says that the team are on the way to finding genetic material (RNA) that could have spontaneously formed from chemical building blocks in an early Earth environment that was then able to replicate itself and essentially begin the process of evolution.

Image of RNA strand (note the single helix structure). Image credit: University of Oregon

There are various theories about the origins of life on Earth and what events occurred to kickstart evolution (if you're interested the various theories I have the basic/common ones explained in a article linked here). One of the current leading theories is RNA replication. RNA is kind of like DNA, which I'm sure everyone is familiar with, but instead of the DNA's famous double helix structure it composed of a single strand. Nonetheless, RNA is able to hold genetic information and fold up to create proteins. The exciting thing about RNA is that it is also able to act as both a catalyst and a template for its own replication. This means that it is able to create a complimentary (sort of opposite) strand of nucleotides (the smaller bits that make up RNA) to itself and then use that as a template to create a new copy of itself. The prospect of RNA replicating itself as a catalyst for the origins of life was first suggest in the 1960s and this study, showing that RNA can create a new copy of itself under lab conditions is the next step in figuring this all out. That being said, we are not there yet. Although the study was able to show RNA generating a complimentary strand and then using that to recreate a copy of itself, the two steps were not achieved in the same container or at the same time, so there is still work to be done to prove that they can happen in sequence as would be needed life's origination.

Looking a bit more in depth at what the study actually did. Gianni and his team started by generating random sequences of nucleotides and from these many options they picked three at random. This simulated the random nature of what might occur naturally in an early Earth setting and removed any bias in choosing the make up of the strands. One of the three strands chosen for the study (known as QT45) was able to demonstrate the ability to self replicate. It is essentially just good luck (as a lot of scientific discoveries often are) that QT45 was one of the three RNA sequences chosen in this study as it may have been the case that none of the the three RNA sequences chosen could self synthesise and QT45 could never have been discovered. It is then also the case that there may be other RNA sequences that can self synthesise but simply have not been studied in this way yet.

QT45 got its name because it is 45 nucleotides long. In previous studies, the only RNA strands that have been seen to self synthesise have been much longer in length, making it hard for them to copy the entirety of themselves as well as making them far less likely to occur randomly in nature. The fact that QT45 is relatively short mitigates both these issues meaning it can fully replicate its entire strand length and has a higher chance of being around due to a random assemblage of nucleotides in early Earth.

Thinking back to the origins of life, the setting for RNA self replication was likely something similar to a hydrothermal vent - where chemical, pH, and temperature gradients around a hot submarine volcano would have been able to provide the necessary conditions for chemical reactions. In Gianni and his team used an alkaline water solution, just above freezing, in their experiment as the conditions for RNA self replication. This could be conditions similar to modern day Iceland, where hydrothermal activity is happening below ice, fitting with the hydrothermal vent hypothesis . It must however, be noted that the team was unable to get both parts of the self synthesis reaction to occur in the same container so the conditions may not have been quite right. Philip Hollinger (from the MRC Laboratory of Molecular Biology) suggested the next steps in this experiment would be to play around with the conditions of reaction to see if more favourable conditions can lead to both steps happening at once. One suggestion is investigating the impact of freeze-thaw cycles, replicating the conditions of a meltwater pocket in ice.

There is still a lot of discovery to be done in figuring out if and how this reaction could have occurred in an early Earth setting but its an promising step in our knowledge of the early evolution of life.

Finally, to bring astrobiology (one of my fav subjects) into this, the possibility of RNA self replication here on Earth means it may also be possible on other planetary bodies. More work needs to be done into the conditions under which this reaction can occur, but as always, research into the beginnings of life on our planet plays a huge role in what locations may be able to host life on other worlds.

Sources:

Science Journal Paper

New Scientist Article