Metavirus

''Metavirus'' is a genus of viruses in the family ''Metaviridae''. They are retrotransposons that invade a eukaryotic host genome and may only replicate once the virus has infected the host. These genetic elements exist to infect and replicate in their host genome and are derived from ancestral elements unrelated from their host. ''Metavirus'' may use several different hosts for transmission, and has been found to be transmissible through ovule and pollen of some plants.

''Metavirus'' contains five families of the ''Ty3/Gypsy'' element with either one or two open-reading frames; these families are ''mdg1, mdg3, blastopia,'' ''412,'' and ''micropia''. Each of the five families contains either one or two open-reading frames, ''gag3'' and/or ''pol3''. There is evidence to support that amino acid deprivation in the elements host genome has frequently caused a frameshift towards the ''Ty3'' element. ''Metavirus'' corresponds with the ''Ogre/Tat'' gene lineage.

Morphology

Species of ''Metavirus'' are single-stranded RNA retrotransposons. They have an icosahedral and linear conformation and are not enclosed in an envelope. Their diameter is approximately 50 nm and they are usually between 42 and 52 nm in length. These genetic elements contain a core and capsid.

Species

The following species are recognized:

* '' Arabidopsis thaliana Athila virus''
* '' Arabidopsis thaliana Tat4 virus''
* '' Bombyx mori Mag virus''
* ''Caenorhabditis elegans Cer1 virus''
* '' Cladosporium fulvum T-1 virus''
* '' Dictyostelium discoideum Skipper virus''
* '' Drosophila buzzatii Osvaldo virus''
* '' Drosophila melanogaster 412 virus''
* '' Drosophila melanogaster Blastopia virus''
* '' Drosophila melanogaster Mdg1 virus''
* '' Drosophila melanogaster Mdg3 virus''
* '' Drosophila melanogaster Micropia virus''
* '' Drosophila virilis Ulysses virus''
* '' Fusarium oxysporum Skippy virus''
* '' Lilium henryi Del1 virus''
* '' Saccharomyces cerevisiae Ty3 virus''
* '' Schizosaccharomyces pombe Tf1 virus''
* '' Schizosaccharomyces pombe Tf2 virus''
* '' Takifugu rubripes Sushi virus''
* '' Tribolium castaneum Woot virus''
* '' Tripneustis gratilla SURL virus''

Evolution

Because of their high mutation and recombination rate and their ability to conduct horizontal gene transfer, the evolutionary history of many retroelements may be challenging to trace (Benachenhou et al., 2013). Scientists often look to the genomes of ''Metavirus'' to compare nucleic acid sequences to the sequences of other viruses, constructing lineages and proposing common ancestors.

Multiple taxa of ''Metavirus'' have genomic sequence that are homologous to other genera of Metaviridae and a suggest common ancestor and/or coevolution. Scientists often look at capsid proteins for evidence of ''Metavirus'' evolution. Much of the lineage of ''Metavirus'' remains unsolved and is presently being researched.

Studies

Mascagni et al. (2017) conducted researched to find homologs and identify strands in sunflower species. In the experiment, DNA was extracted from various helianthus species and the genomes of retrotransposons were identified using BLASTX analysis. Phylogenetic trees were constructed using neighbor-joining clustering method and a bioinformatic pipeline was constructed to allow genomic analysis. Two elements, ''SURE'' and ''Helicopia,'' were identified and placed into the ''Gypsy'' and ''Copia'' superfamilies, respectively. Thus, the ''SURE'' element belongs to the ''Gypsy'' group, of the ''Ogre/Tat'' lineage, of the genus ''Metavirus''. Further analysis led Mascagni et al. (2017) to identify mutations and conclude that the ''Metavirus'' lineage evolved before ''Sirevirus.'' Mascagni et al. (2017) also found evidence that the ''SURE'' elements and ''Helicopia'' elements had hybridized, potential for new lineages.

Nefedova and Kim (2009), conducted a study on ''Drosophila melanogaster'' to further identify lineages of ''Metavirus''. Homologs were identified from previously extracted DNA of retrotransposons and ''Drosophila melanogaster'' and phylogenetic trees were constructed. ''Metaviruses'' possess the env gene, allowing them to be infective, which Nefedova and Kim (2009) concluded was obtained from horizontal gene transfer from baculoviruses. ''Metavirus'' contains the roo element which is thought to have been obtained from gene transfer from '' Errantivirus,'' or more likely, the two genera share a common ancestor.

References

External links

ICTV Report: ''Metaviridae''
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Descriptions of Plant Viruses

{{Taxonbar, from=Q18819496

Metaviridae
RNA reverse-transcribing viruses
Virus genera