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Survival of RNA Replicators Is Much Easier in Protocells Than in Surface-Based, Spatial Systems

1
Origins Institute and Department of Physics and Astronomy, McMaster University, Hamilton, ON L8S 4L8, Canada
2
Origins Institute and Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8S 4L8, Canada
*
Author to whom correspondence should be addressed.
Received: 11 April 2019 / Revised: 24 July 2019 / Accepted: 30 July 2019 / Published: 7 August 2019
(This article belongs to the Special Issue Themed Issue Commemorating Prof. David Deamer's 80th Birthday)
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Abstract

In RNA-World scenarios for the origin of life, replication is catalyzed by polymerase ribozymes. Replicating RNA systems are subject to invasion by non-functional parasitic strands. It is well-known that there are two ways to avoid the destruction of the system by parasites: spatial clustering in models with limited diffusion, or group selection in protocells. Here, we compare computational models of replication in spatial models and protocells as closely as possible in order to determine the relative importance of these mechanisms in the RNA World. For the survival of the polymerases, the replication rate must be greater than a minimum threshold value, kmin, and the mutation rate in replication must be less than a maximum value, Mmax, which is known as the error threshold. For the protocell models, we find that kmin is substantially lower and Mmax is substantially higher than for the equivalent spatial models; thus, the survival of polymerases is much easier in protocells than on surfaces. The results depend on the maximum number of strands permitted in one protocell or one lattice site in the spatial model, and on whether replication is limited by the supply of monomers or the population size of protocells. The substantial advantages that are seen in the protocell models relative to the spatial models are robust to changing these details. Thus, cooperative polymerases with limited accuracy would have found it much easier to operate inside lipid compartments, and this suggests that protocells may have been a very early step in the development of life. We consider cases where parasites have an equal replication rate to polymerases, and cases where parasites multiply twice as fast as polymerases. The advantage of protocell models over spatial models is increased when the parasites multiply faster. View Full-Text
Keywords: RNA World; polymerase; error threshold; protocell; membranes; spatial lattice model; evolution of cooperation; parasites RNA World; polymerase; error threshold; protocell; membranes; spatial lattice model; evolution of cooperation; parasites
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Shah, V.; de Bouter, J.; Pauli, Q.; Tupper, A.S.; Higgs, P.G. Survival of RNA Replicators Is Much Easier in Protocells Than in Surface-Based, Spatial Systems. Life 2019, 9, 65.

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