Nudivirus

Nudiviruses are a family of animal viruses that constitute the family ''Nudiviridae''. Insects and marine crustaceans serve as natural hosts. There are 11 species in this family, assigned to 4 genera. Diseases associated with this family include: death in larvae, chronic disease in adults.

Structure and life cycle

Nudiviruses are characterized by rod-shaped and enveloped nucleocapsids and they replicate in the nucleus of infected host cells. In some parasitoid wasp species, a nudivirus genome, in proviral form, is integrated into the wasp genome and produces virus like particles called polydnaviruses that are injected into lepidopteran larvae and are thought to facilitate parasitization of the larvae. Nudiviruses infect only insects and marine crustaceans.

Transmission of nudiviruses occurs generally by feeding or mating. Infections can be lethal for the larvae and can possibly reduce the fitness of the host by reducing offspring production and survival among adults.Unckless RL. (2011) A DNA Virus of ''Drosophila''. Published online 2011 October 28

Taxonomy

The family ''Nudiviridae'' contains the following genera:

*'' Alphanudivirus''
*'' Betanudivirus''
*'' Deltanudivirus''
*'' Gammanudivirus''

Phylogeny

Gene content comparison and phylogenetic analyses show that nudiviruses share 20 core genes with baculoviruses and form a monophyletic sister group with them. Fossil calibration estimate this association arose 100 million years ago(Mya), while the last common ancestor of BVs, nudiviruses, and baculoviruses existed approximately 312 Mya. Baculoviruses and nudiviruses differ in gene content, genome organization, cytopathology, infection of adults and most likely in host range. The 20 core genes common in both baculoviruses and nudiviruses are involved in RNA transcription, DNA replication, virion structural components and many other functions. Gene content and sequence similarity suggest that the nudiviruses GbNV, HzNV-1, and OrNV form a monophyletic group of nonoccluded double-stranded DNA viruses, which separated from the baculovirus lineage before this radiated into dipteran-, hymenopteran-, and lepidopteran-specific clades of occluded nucleopolyhedroviruses and granuloviruses.

Host-virus relations

*''Drosophila innubila nudivirus'' – ''Drosophila innubila'' (''Diptera'')
*''Gryllus bimaculatus'' nudivirus – black cricket (''Teleogryllus commodus'')
*''Helicoverpa zea'' nudivirus 1 – cotton bollworm
* ''Helicoverpa zea'' nudivirus 2 – cotton bollworm
*''Homarus gammarus nudivirus'' - European lobster (''Homarus gammarus'')
*''Oryctes rhinoceros nudivirus'' – rhinoceros beetle '' Oryctes rhinoceros''
*''Penaeus monodon'' nudivirus – black tiger shrimp
*''Dikerogammarus haemobaphes'' nudivirus – an amphipod crustacean (''Dikerogammarus haemobaphes'')

Defense mechanisms

In many organisms, apoptosis can be regarded as an early defense mechanism against viral infection. Some viral genes allow the cell to survive for longer while producing more virions; ''Heliothis zea'' Nudivirus 1 (HzNV-1 or Hz-1 virus), a nudivirus with a broad host range, has been shown to block an induced-apoptosis gene (''hhi1''). A functional anti-apoptosis gene, (Hz-iap2), has been found to suppress the ''hhi1'' gene which can cause the cell to die. A second inhibitor gene (Ac-iap2) to the ''hhi1'' gene has been also discovered, but its function is still uncertain.

Nudivirus encoded microRNAs

Micro RNAs (miRNAs) are small non-coding RNA molecules that play important roles in the regulation of genes in eukaryotic organisms. Virus encoded miRNAs are commonly reported in DNA viruses and several nudiviruses have been reported to encode miRNAs. The first reported nudivirus encoded miRNA was from Heliothis zea nudivirus-1 which was shown to regulate virus latency. Two other viruses ''Drosophila innubila nudivirus'' and ''Oryctes rhinoceros nudivirus'' have also been reported to encode miRNA molecules from transcriptomic studies, however the role of these miRNAs and their role in virus-host interactions is yet to be experimentally determined.

History

In 2007, the genus ''Nudivirus'' was proposed to include viruses similar to the ''Oryctes rhinoceros'' virus. Nudiviruses were classified as the family ''Nudiviridae'' in 2013.ICTV proposals 2013.003a-KI et al.
J. E. Jehle et al. Retrieved 21 November 2015.

Etymology

The word "nudivirus" comes from the Latin ''nudus'', which means naked and ''virus'', poison. Naked refers to the fact that most do not have the dense protein bodies which surround baculoviruses. However occluded nudiviruses, with such protein bodies, such as those of ''Tipula oleracea'' and ''Penaeus monodon'' have been characterized.

References

{{Taxonbar, from=Q18811654

Nudiviridae
Virus families