Viriforms-A New Category of Classifiable Virus-Derived Genetic Elements

Area of Science:

• Virology
• Genetics
• Evolutionary Biology

Background:

• The International Committee on Taxonomy of Viruses (ICTV) has established "viriforms" as a novel category for virus-derived genetic elements.
• Viriforms represent endogenized viruses exapted by host cells for essential life cycle functions.

Purpose of the Study:

• To introduce and define the new polyphyletic category of viriforms.
• To outline the properties of diverse known viriform groups and proposed classification frameworks.

Main Methods:

• Review of recent discoveries and existing literature on virus-derived genetic elements.
• Analysis of the characteristics and functions of viriforms in different organisms.
• Examination of proposed International Committee on Taxonomy of Viruses (ICTV) classification frameworks.

Main Results:

• Viriforms are distinct from viruses, viroids, and satellite nucleic acids, characterized by packaging host genetic material instead of their own genomes.
• Diverse viriforms include Polydnaviriformidae in wasps and gene transfer agents (GTAs) in prokaryotes, with potential presence in mammalian genomes.
• The ICTV is developing classification frameworks for these newly recognized elements.

Conclusions:

• Viriforms represent a significant expansion of our understanding of virus-host interactions and genetic element evolution.
• The establishment of viriforms and their classification frameworks by the ICTV provides a basis for future research into these unique genetic entities.