Densovirinae


Densovirinae is a subfamily of single-stranded DNA viruses in the family Parvoviridae. The subfamily currently has 8 recognized genera and 17 species. Densoviruses are known to infect members of insect orders Blattodea, Diptera, Hemiptera, Hymenoptera, Lepidoptera, and Orthoptera, while some viruses infect and multiply in crustceans such as shrimp or crayfish, or sea stars from phylum Echinodermata.

Virology

Densoviruses are small and non enveloped. Virions are icosahedral in shape with triangulation number = 1. There are 60 copies of the coat protein in the virion. Each copy has a shape described as a "quadrilateral 'kite-shaped' wedge", and the appearance of the surface is rough with many small projections. Virions do not appear to contain lipids.
Genomes are non-segmented, about 4–6 kilobases in length and usually contain two or three open reading frames. The 5' open reading frame encodes two nonstructural proteins and the 3' open reading frame encodes two or three capsid proteins. Both the 5' and 3' termini have hairpin loops. If a third open reading frame is present it encodes a second non structural protein. The genome is anmbisense, encoding proteins on both the positive sense and negative sense directions. Transcriptional regulation and post-transcriptional modification are used to produce different nonstructural proteins and structural proteins.
Virions enter the host cell is achieved by attachment to host receptors, which may be mediated by clathrin-mediated endocytosis or clathrin-independent dynamin-dependent endocytosis. The NS-1 protein has a superfamily 3 DNA helicase and an HuH endonuclease motif. These motifs are common in small DNA viruses. The proteins that contain these motifs bind to the viral origins of replication and unwind and nick these origins, allowing access by the host's proteins to the viral genome for replication and transcription. The genome is replicated by a unique rolling hairpin mechanism. DNA-templated transcription, with some alternative splicing mechanism is the manner of transcription.

Taxonomy

Eight genera are currently recognized, containing a combined 17 species:
Ambidensovirus was previously recognized as a genus, but in 2019 it was split into the six genera prefixed with Aqu-, Blatt-, Hemi-, Pefu-, Proto-, and Scindo-.