Evolution Experiment With Translation-Coupled RNA Replication System

Abstract

The ability to evolve is a key characteristic that distinguishes living things from non-living chemical compounds. The construction of an evolvable cell-like system from non-living molecules has been a major challenge. We encapsulated an artificial RNA genome and the factors for protein synthesis into water droplets in oil or lipid vesicles to develop an evolvable artificial cell model. In the micro-compartments, the artificial genomic RNA replicates through the translation of its encoding RNA replicase gene. Using the translation-coupled RNA replication system, we performed a long-term (600-generation) evolution experiment, in which mutations were spontaneously introduced by the translated replicase into its genetic information. At the beginning, the amplified RNA genomes were in the double stranded form, a dead-end product for the translation while a small parasitic RNA appeared by a deletion mutation on the RNA genome and dominated the population by stealing the replicase translated from the RNA genome. But highly replicable mutant RNA genomes gradually evolved to eliminate the two short circuits by reinforcing the interaction with the translated replicase. At the end, two-order acceleration in replication rate was observed whereas the population declined when the same reaction was conducted in a bulk solution. The results indicated that the micro-compartmentalization was essential for the assembly of the bio-polymers to evolve.