The development of complex life on the harsh early Earth raises the question of how such a feat was possible. The key lies in the presence of ribonucleic acid (RNA) at the outset, serving as the carrier of the initial genetic information. To enhance the complexity of RNA sequences, these biomolecules require the release of water—a challenging task in the predominantly seawater-covered primitive Earth.
In a recent publication in the Journal of the American Chemical Society (JACS), researchers led by LMU professor Dieter Braun shed light on RNA’s interaction with water and how its inherent recycling capabilities, coupled with specific environmental conditions, could have played a crucial role in the emergence of life.
According to Braun, who heads the Collaborative Research Center (CRC) Molecular Evolution in Prebiotic Environments and coordinates activities at the ORIGINS Excellence Cluster, the process of RNA synthesis involves the release of a water molecule for every bond formed within the RNA chain. Conversely, the addition of water to an RNA molecule leads to the disassembly of the chain, returning the RNA building blocks to the prebiotic pool. This dynamic equilibrium is particularly effective under low-saline conditions with elevated pH levels, mirroring the conditions prevalent on the early Earth.
The study’s lead author, Adriana Serrão, highlights that RNA, under such conditions, can undergo splitting without the need for additional water molecules. This unique property allows the RNA strand to regenerate without water involvement, facilitating the formation of new RNA bonds. The experiments conducted by Braun’s team demonstrate the efficiency and precision of this RNA splitting and rejoining process in replicating sequence information.
Contrary to previous assumptions that RNA replication necessitates the presence of complex ribozymes in saline environments, the research indicates that simple RNA sequences can self-replicate efficiently without the need for elaborate structures. This discovery challenges the notion that long ribozyme sequences were essential in the early stages of RNA evolution.
The study’s co-lead author, Sreekar Wunnava, emphasizes that the precision of RNA copying in this manner rivals that achieved by ribozymes, suggesting that early life could have emerged without the requirement for lengthy complex sequences. The metabolic process of early life involved the continuous copying of RNA sequences through the replacement of molecules, thriving in alkaline freshwater environments akin to those found on volcanic islands like Hawaii and Iceland.
In conclusion, the study posits that life could have originated from a rudimentary RNA-based system in a cold, alkaline prebiotic environment. Despite the slow pace of reactions under such conditions, the availability of time during the early stages of evolution, coupled with the sheltered freshwater niches on volcanic islands, provided a conducive setting for RNA survival and replication on the otherwise hostile early Earth.