Oscillation dynamics of host-parasite population in an artificial self-replication system

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Yohsuke Bansho, Norikazu Ichihashi, Tetsuya Yomo

Osaka University, Japan

The appearance of parasite is one of the largest hurdles for primitive self-replicators in prebiotic evolution because once a parasite appears, it amplifies relying on host’s components until inhibiting the replication of the host. It casts a question: how has the primitive self-replication been established under threats of parasites? To understand this question, we are attempted to construct the artificial host-parasite interacting self-replication system in vitro from non-living molecules. We used an artificial self-replication system of RNA derived from RNA phage Q beta, in which RNA replicase is translated from the artificial genome RNA and replicates the RNA. This self-replication system, however, has problems in the efficiency and recursiveness caused by amplification of parasite RNA, a shortened RNA which lost replicase gene. The parasite is replicated rapidly because of its shorter length, resulting in competitive inhibition of the genome replication. We performed long-term self-replication reaction of this artificial host-parasite system in a cell-like compartment (water in oil emulsion), and found that the populations of the host and the parasite oscillate. The oscillation of the host was followed by the oscillation of the parasite like predator-prey system, but driven by the different mechanism, compartmentalization of the parasite into a minor fractions of the emulsion. Our result demonstrated that a primitive self-replication system sustains even in the presence of parasites in compartment structure at appropriate dilution rate. Moreover, the sequencing analysis on the host genomic RNA revealed that frequent changes of the genetic sequence occurred during the oscillation. It might suggest that this parasite-driven oscillation dynamics facilitates the evolution of the host RNA.