Proposals that RNA played a central role during the emergence and early evolution of life are based in part on the fact that RNA can both store hereditary information and catalyze chemical reactions. In vitro evolution studies provide a tool for assessment of the potential of RNA to support biological function during early evolution of life. A limitation of these studies lies in the fact that they do not reflect the wide range of potential environments encountered by emerging life. To test the impact of environmental factors on RNA’s potential to function in the earliest forms of life as well as in extant life, we evolved populations of catalytic RNAs (ribozymes) in multiple environments. We evolved ribozymes in the presence of different metal ions, at multiple pH values, in the presence of a mineral surface, and with molecular crowding agents. Our populations of in vitro evolved ribozymes are sensitive to both pH and metal ion identity, and exhibit a pH-dependent metal ion specificity. Our populations of ribozymes evolved in crowded conditions, retain activity in dilute solutions. Alternatively, populations evolved in dilute solutions show diminished activity in the presence of crowding agents. In contrast, the presence of a clay mineral surface has surprisingly little effect on the evolution and activity of ribozymes. Our results highlight the importance of considering the specific environments in which functional biopolymers evolve when evaluating their roles in extant biology or their potential roles in the origin and early evolution of life.
Point of contact: mark.a.ditzler@nasa.gov