Sustainable replication and coevolution of cooperative RNAs in an artificial cell-like system

Cooperation among independently replicating molecules is a key phenomenon that allowed the development of complexity during the early evolution of life. Generally, this process is vulnerable to parasitic or selfish entities, which can easily appear and destroy such cooperation. It remains unclear how this fragile cooperation process appeared and has been sustained through evolution. Theoretical studies have indicated that spatial structures, such as compartments, allow sustainable replication and the evolution of cooperative replication, although this has yet to be confirmed experimentally. In this study, we constructed a molecular cooperative replication system, in which two types of RNA, encoding replication or metabolic enzymes, cooperate for their replication in compartments, and we performed long-term replication experiments to examine the sustainability and evolution of the RNAs. We demonstrate that the cooperative relationship of the two RNAs could be sustained at a certain range of RNA concentrations, even when parasitic RNA appeared in the system. We also found that more efficient cooperative RNA replication evolved during long-term replication through seemingly selfish evolution of each RNA. Our results provide experimental evidence supporting the sustainability and robustness of molecular cooperation on an evolutionary timescale.