On the emergence of structural complexity in RNA replicators

Area of Science:

• Origins of Life Research
• Molecular Evolution
• Biophysics

Background:

• The RNA world hypothesis posits that RNA was central to early life.
• Complex RNA structures are crucial for biological functions.
• Existing evolutionary models often require specific environmental conditions.

Purpose of the Study:

• To investigate a simple, parsimonious model for the emergence of complex RNA structures.
• To determine if undirected replication can lead to functional RNA structures.
• To explore the role of GC content in RNA structural complexity.

Main Methods:

• Computational study of 50-nucleotide RNA sequences.
• Mapping energetically stable structures on complete mutational networks.
• Analysis of RNA secondary structures at varying GC content regimes.

Main Results:

• Undirected replication at specific GC content regimes generates multibranched RNA secondary structures.
• Stable structures in the sequence landscape are enriched with multibranched forms.
• This enrichment occurs at a length scale consistent with complex structures in RNA databases.

Conclusions:

• A random replication mechanism with 50% GC content can explain the natural enrichment of complex RNA structures.
• Directed evolution towards the most stable folds aids multibranched structure formation at high GC content.
• Simple, undirected processes may be sufficient for generating foundational molecular complexity in early life.