Genotype network intersections promote evolutionary innovation.

Area of Science:

• Evolutionary biology
• Genetics
• Biochemistry

Background:

• Evolutionary innovations are novel traits that enhance biodiversity, but their genetic underpinnings are not well understood.
• Analyzing genotype networks, which link genetic variants to phenotypes, is crucial for a systems-level understanding of innovation.
• Innovations can emerge at the convergence of distinct genotype networks, yet experimental analysis is challenging due to the sheer number of genetic variants.

Purpose of the Study:

• To investigate the fitness landscape at the intersection of genotype networks for two catalytic RNA molecules (ribozymes).
• To explore how functional overlap and network structure influence the emergence and adaptation of new functions.

Main Methods:

• Utilized high-throughput sequencing to map the fitness landscape of numerous RNA sequences.
• Assessed the catalytic abilities of RNA variants for two distinct chemical reactions.
• Employed evolutionary simulations to model adaptation dynamics within genotype networks.

Main Results:

• Identified extensive functional overlap between the genotype networks of the two ribozymes, with many sequences exhibiting dual catalytic activity.
• Demonstrated that intersecting genotype networks provide numerous pathways for discovering new functions.
• Found that the rate of adaptation to a new function is influenced by the local ruggedness of the genotype network and can be accelerated by neutral evolution.

Conclusions:

• Overlapping genotype networks are a key feature of fitness landscapes that facilitate evolutionary innovations.
• Neutral evolution can enhance adaptation rates by enabling populations to explore diverse regions of the genotype network.
• The findings suggest that intersecting genotype networks may have played a significant role in historical evolutionary innovations.