Sprecher
Beschreibung
A way to study the emergence of life is to create a physico-chemical system that is capable of open ended evolution. The aim is to search for most minimal requirements to maximize the probability to find it outside the lab. Starting life with three molecules in a one-pot geological non-equilibrium without human intervention would be a favorable scenario.
We revisited polymerization and templated ligation of RNA from nucleotides with 2’,3’ cyclic phosphates. Simple alkaline conditions at pH 9-11 without catalysts or added salts oligomerized the nucleotides up to 10mers over across 25-80°C within a day, both in the ‘dry’ state or in the wet-dry cycling at a heated air-water interface [1]. The polymerization was dominated by G, but cold and dry conditions, achieved in the planet simulator of McMaster University yielded random sequences of GC or GCAU according to mass spectrometry.
Interestingly, the same conditions triggered (i) with Trimetaphosphate the specific cyclic phosphorylation and (ii) the templated ligation of oligonucleotides, the latter also under ‘dry’ conditions. Therefore, we envisage a dry RNA world where exponential replication is driven by long enough polymers, templated ligation and hydrolytic recombination using wet-dry cycles to separate the strands. Short, replicated RNA sequences could enhance their own ligation and start the first cycle of functional RNA evolution.
That CO2-water interfaces can drive the replication towards sequence lengths of up to 1300mers was demonstrated recently [2]. The accumulation by capillary flow overcame the tyranny of the shortest. The long strands were shown to separate under the pH cycling provided by the Hadean atmosphere of CO2. While the replication was still implemented by a polymerase to enhance kinetics, the findings indicate that a similar strand separation will be possible for RNA based replication even under intermediate Mg2+ concentrations.
References:
[1] Dass AV, Wunnava S, Langlais J, von der Esch B, Krusche M, Ufer L, et al. RNA auto-polymerisation from 2’,3’-cyclic nucleotides at air-water interfaces. ChemRxiv. Cambridge: Cambridge Open Engage (2022). https://doi.org/10.26434/chemrxiv-2022-zwh2t
[2] Ianeselli, A., Atienza, M., Kudella, P.W. et al. Water cycles in a Hadean CO2 atmosphere drive the evolution of long DNA. Nat. Phys. (2022). https://doi.org/10.1038/s41567-022-01516-z
