Abstract
BackgroundRNA or RNA-like polymers are the most likely candidates for having played the lead roles on the stage of the origin of life. RNA is known to feature two of the three essential functions of living entities (metabolism, heredity and membrane): it is capable of unlimited heredity and it has a proven capacity for catalysing very different chemical reactions which may form simple metabolic networks. The Metabolically Coupled Replicator System is a class of simulation models built on these two functions to show that an RNA World scenario for the origin of life is ecologically feasible, provided that it is played on mineral surfaces. The fact that RNA templates and their copies are of complementary base sequences has an obvious dynamical relevance: complementary strains may have very different structures and, consequently, functions – one may specialize for increasing enzymatic activity while the other takes the role of the gene of the enzyme.ResultsIncorporating the functional divergence of template and copy into the Metabolically Coupled Replicator System model framework we show that sequence complementarity 1) does not ruin the coexistence of a set of metabolically cooperating replicators; 2) the replicator system remains resistant to, but also tolerant with its parasites; 3) opens the way to the evolutionary differentiation of phenotype and genotype through a primitive version of phenotype amplification.ConclusionsThe functional asymmetry of complementary RNA strains results in a shift of phenotype/genotype (enzyme/gene) proportions in MCRS, favouring a slight genotype dominance. This asymmetry is expected to reverse due to the evolved trade-off of high “gene” replicability and high catalytic activity of the corresponding “enzyme” in expense of its replicability. This trade-off is the first evolutionary step towards the “division of labour” among enzymes and genes, which has concluded in the extreme form of phenotype amplification characteristic of our recent DNA-RNA-protein World.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-014-0234-8) contains supplementary material, which is available to authorized users.
Highlights
RNA or RNA-like polymers are the most likely candidates for having played the lead roles on the stage of the origin of life
All simulations were initiated with 80% of the sites occupied at random positions by the “genotype” and “phenotype” forms of all replicator types, with both complementary forms of each replicator species represented at equal (10-10%) proportions
The three most effective determinants of coexistence were all related to spatial mixing in that model: the speed of replicator diffusion (D) and the size of replication neighbourhoods (r) both correspond to replicator mobility, whereas metabolic neighbourhood size (h) is the proxy for the average distance that metabolite molecules can cover on the surface before being used in a reaction, degraded or desorbed from the surface
Summary
RNA or RNA-like polymers are the most likely candidates for having played the lead roles on the stage of the origin of life. The crucial advantage of rarity comes from the local nature of metabolic interactions on the mineral surface: rare metabolic replicator types have a higher chance to find at least one copy of the more common species within the surface-diffusion range of the metabolites than the common ones to have at least one rare type copy nearby (Additional file 1: Figure S1). This simple spatial regulatory mechanism has been shown to maintain robust coexistence in spite of vast differences assumed in the replicabilities of the different replicator species [1,6]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
