Varidnaviria !
Introduction to Varidnaviria
Varidnaviria is a realm of viruses that encompasses all DNA viruses encoding major capsid proteins (MCP) containing a vertical jelly roll fold. These MCPs form pseudohexameric subunits of the viral capsid, which houses the viral deoxyribonucleic acid (DNA), and are oriented perpendicular, or vertical, to the surface of the capsid. In addition to the unique structure of the MCP, viruses in the realm also share other key characteristics, such as minor capsid proteins (mCP) with the same vertical jelly roll fold, an ATPase responsible for packaging the viral DNA into the capsid, and a DNA polymerase that replicates the viral genome. These shared features are the basis for the classification of viruses in the Varidnaviria realm.
Classification and Evolution of Varidnaviria
The realm Varidnaviria was established in 2019, based on the distinctive shared characteristics among the viruses in this group. The realm is divided into two main groups: viruses with a double vertical jelly roll (DJR) fold in their MCP, which belong to the kingdom Bamfordvirae, and viruses with a single vertical jelly roll (SJR) fold in their MCP, classified under the kingdom Helvetiavirae. It is thought that the DJR-MCP lineage evolved from the SJR-MCP lineage through a gene fusion event. The SJR-MCP viruses show a close relation to nucleoplasmins, suggesting a potential origin of the jelly roll fold in the MCPs of the Varidnaviria realm. Most eukaryotic DNA viruses are found within this realm.
Ecological and Medical Importance
Marine viruses within Varidnaviria are abundant across the globe and play a crucial role in marine ecology. Many viruses in this realm are associated with diseases in animals, including adenoviruses, poxviruses, and the African swine fever virus. Poxviruses have had significant historical and medical importance, particularly in the eradication of smallpox, which was caused by the Variola virus, the first disease to be eradicated by a vaccine. Additionally, the realm includes giant viruses, which are unusually large, both in size and the number of genes they contain, making them an area of increasing interest in virus research.
