Adaptation and Diversification of an RNA Replication System under Initiation- or Termination-Impaired Translational Conditions.

Adaptation to various environments is a remarkable characteristic of life. Is this limited to extant complex living organisms, or is it also possible for a simpler self-replication system to adapt? In this study, we addressed this question by using a translation-coupled RNA replication system that comprised a reconstituted translation system and an RNA "genome" that encoded a replicase gene. We performed RNA replication reactions under four conditions, under which different components of translation were partly inhibited. We found that replication efficiency increased with the number of rounds of replication under all the tested conditions. The types of dominant mutations differed depending on the condition, thus indicating that this simple system adapted to different environments in different ways. This suggests that even a primitive self-replication system composed of a small number of genes on the early earth could have had the ability to adapt to various environments.