Virus world as an evolutionary network of viruses and capsidless selfish elements

Area of Science:

• Virology
• Evolutionary Biology
• Genetics

Background:

• Viruses are traditionally defined as capsid-encoding organisms, distinct from cellular life.
• Homologous capsids in diverse viruses suggest ancient viral lineages.
• Viral evolution is modular, with hallmark genes found across different viral types.

Purpose of the Study:

• To propose the concept of a "greater virus world" encompassing both capsid-encoding viruses and capsidless genetic elements.
• To redefine the fundamental nature of viruses beyond capsid presence.
• To explore the evolutionary network of viruses and selfish genetic elements.

Main Methods:

• Review of existing literature on viral structure, genetics, and evolution.
• Analysis of shared conserved genes between viruses and other replicons.
• Theoretical considerations of replicator dynamics and parasitic emergence.

Main Results:

• Capsidless selfish genetic elements (plasmids, transposons) share hallmark genes with viruses.
• Viruses and capsidless elements have likely evolved from each other multiple times.
• The earliest precellular life likely involved capsidless genetic parasites.

Conclusions:

• The "greater virus world" is an evolutionary network linked by shared genes.
• The defining characteristic of this world is genetic parasitism, not the presence of a capsid.
• Viruses and related elements represent diverse degrees of reliance on host information systems.