[S10-4] Diversification through coevolution between artificial self-replicating and parasitic RNAs
To understand a possible evolutionary process toward present-day living organisms, we have constructed an evolvable RNA replication system in an artificial cell-like structure and are investigating the evolutional process through a long-term replication experiment. The first interesting phenomenon that we observed is the appearance of parasitic RNA, which lost the replicase gene encoded in the original RNA and thus has to rely on the replicase produced from other RNAs. The parasitic RNA produces oscillating population dynamics. The original RNA (i.e., host RNA) next evolved to be resistant to the parasitic RNA by changing the encoded replicase, and then a new type of parasite, which overcomes the host resistance, appeared. Again, the host RNA developed a new method to be resistant to the new parasite, and then a different parasite appeared to infect the new host. In this manner, the evolutionary arms race occurred between host and parasitic RNAs. This coevolutionary process also produced diversity in the host and parasitic species. The host and parasitic RNAs diverged into two lineages and coexist for a long period. These results suggest that coevolution with parasitic entities allows the continuous evolution, producing the diversity of self-replicating species. Parasites may play an important role in the evolution of life.