Circular at the very beginning: on the initial genomes in the RNA world

Area of Science:

• Origin of life studies
• Molecular evolution
• Astrobiology

Background:

• The RNA world hypothesis posits RNA served as both genetic material and catalyst.
• A division of labor between genome replication and catalytic function (ribozymes) is proposed.
• Linear RNA is favored for ribozyme folding, while circular RNA may be better for templating and resisting degradation.

Purpose of the Study:

• To computationally model a precellular RNA world scenario.
• To investigate the maintenance and evolution of a circular RNA genome with linear ribozymes.
• To explore the transition from single-gene to multi-gene systems.

Main Methods:

• Computer simulations of RNA genome replication and ribozyme production.
• Modeling of a one-gene system with a circular genome and linear ribozyme.
• Analysis of a two-gene system and potential evolutionary pathways.

Main Results:

• A one-gene circular RNA system showed low efficiency in producing ribozymes, requiring precise chain manipulation.
• Introducing noncoding sequences allowed for gene duplication via mutation, potentially improving efficiency.
• A two-gene system demonstrated improved function, with ribozymes aiding circular genome replication.

Conclusions:

• Circular RNA genomes may have been advantageous in the early RNA world.
• The evolution of multi-gene circular genomes could have been facilitated by noncoding sequences.
• This model provides a potential origin for the prevalence of circular genomes in modern life.