A team of chemists based in Munich demonstrated that the alternation of wet and dry conditions on the Earth of origin would be sufficient to initiate prebiotic synthesis of ANN nucleotides present in all domains of life.
As our knowledge of the conditions on the primordial Earth grows, the evolution of RNA and DNA some 4 billion years ago is still shrouded in mystery.
What was the origin of the chemical structures that make up the subunits of what we now know as “hereditary molecules”, RNA and DNA?
These molecules connected in long chains that not only coded the information, but reproduced and transmitted it: how did all this begin?
Research is underway to find out more about the chemical evolution that preceded the first biological cells.
Research conducted at the Ludwig-Maximilians-Universitaet (LMU) in Munich, Germany, partly supported by the EU EPiR project, is trying to fill this fascinating gap in our knowledge and the team’s latest findings have been published in “Nature“.
By exposing simple chemicals to the types of fluctuating physical conditions that would have occurred in geothermically active areas of our planet billions of years ago, such as those caused by volcanic activity, researchers have demonstrated the possibility of nucleotide formation in a continuous process.
A cauldron of ingredients that gives birth to life.
They started with a mixture of the elements that, in the past, have been shown to form simple precursors under probiotic conditions: formic acid, sodium nitrite, acetic acid and some compounds containing nitrogen.
The reaction mixture also contained iron and nickel, both abundant in the earth’s crust. They then subjected everything to fluctuations in temperature, pH and humidity to imitate primordial conditions, such as those due to highly variable seasonal temperatures.
The team built on the work done last year, not only starting with simple precursor compounds, but also deciding to replicate conditions that should prevail in a plausible geological context, such as hydrothermal springs on land.
By combining these ingredients and subjecting them to conditions that mimic the geology and meteorology of the original Earth, the team discovered that a series of reactions gave rise to compounds called formamidopyrimidines.
This is a crucial discovery, as these compounds can turn into adenosine and guanosine, both components of DNA.
A whole series of related molecules has also been synthesised.
As it has been argued, “It is even more surprising that all the observed modifications occur in the ANNs of all three domains of life – Eukaryotes (animals and plants), Bacteria and Archaea – and are therefore essential components of functional genetic systems“.
Based on the results obtained, researchers believe it is very likely that the compounds were present in the last common ancestor of all life forms.
This in turn, they say, “(…) suggests that these compounds must have been available on the primordial Earth when biological evolution began.
EPiR explains that the genetic code consists of a defined sequence of four canonical nucleotides and that the sequence of these bases contains the structure of all life on earth.
It is clear that this sequence information alone is not enough to explain how a multicellular organism can generate specialised cells such as the 200 types of cells in the human body that we know.
This, explains EPiR, requires a second level of information which, it has been discovered, is based mainly on chemistry.
More than 150 chemical derivatives of RNA nucleotides are known and there are still many to discover.
This is why EPiR is studying the modifications of ANN to decipher its functions.
For more information, see: CORDIS project website