View source for Sigmavirus

{{Short description|Genus of viruses}}
{{Use dmy dates|date=April 2017}}
{{Virusbox
| taxon = Sigmavirus
}}
'''''Sigmavirus''''' is a genus of [[viruses]] in the family ''[[Rhabdoviridae]]'', order ''[[Mononegavirales]]''. Sigmaviruses naturally infect [[dipterans]].<ref name=ViralZone>{{cite web|title=Viral Zone|url=http://viralzone.expasy.org/all_by_species/4656.html|publisher=ExPASy|access-date=13 August 2015}}</ref><ref name=ICTV>{{cite web |title=Virus Taxonomy: 2020 Release |url=https://ictv.global/taxonomy |publisher=International Committee on Taxonomy of Viruses (ICTV) |date=March 2021 |access-date=18 May 2021}}</ref> It is not to be confused with the Mega Man character of the same name.
==Taxonomy==
The genus contains the following species:<ref name=ICTV />
* ''[[Capitata sigmavirus]]''
* ''[[Domestica sigmavirus]]''
* ''[[Drosophila affinis sigmavirus]]''
* ''[[Drosophila ananassae sigmavirus]]''
* ''[[Drosophila immigrans sigmavirus]]''
* ''[[Drosophila melanogaster sigmavirus]]''
* ''[[Drosophila obscura sigmavirus]]''
* ''[[Drosophila tristis sigmavirus]]''
* ''[[Hippoboscid sigmavirus]]''
* ''[[Hubei sigmavirus]]''
* ''[[Lousefly sigmavirus]]''
* ''[[Muscina stabulans sigmavirus]]''
* ''[[Myga sigmavirus]]''
* ''[[Shayang sigmavirus]]''
* ''[[Sturtevanti sigmavirus]]''
* ''[[Wuhan sigmavirus]]''
* ''[[Ying sigmavirus]]''
==Discovery==
Drosophila melanogaster sigmavirus (DMelSV) was discovered by a group of French researchers in 1937 <ref>{{cite journal | last1 = L'Heritier | first1 = P. H. | last2 = Teissier | first2 = G. | year = 1937 | title = Une anomalie physiologique héréditaire chez la Drosophile | journal = C. R. Acad. Sci. Paris | volume = 231 | pages = 192–194 }}</ref> after they observed certain fly lines became paralysed and died on exposure to carbon dioxide (which is commonly used as an anesthetic for ''[[Drosophila]]''). They found the carbon dioxide sensitivity was caused by an infectious agent which they named sigma, and was later found to be a rhabdovirus.<ref>{{cite book | last1 = L'Heritier | first1 = P | title = Advances in Virus Research Volume 5 | year = 1957 | chapter = The hereditary virus of Drosophila | journal = Advances in Virus Research | volume = 5 | pages = 195–245 | doi = 10.1016/S0065-3527(08)60674-0 | pmid = 13508405 | isbn = 9780120398058 }}</ref> More recently new sigmaviruses have been discovered in diptera of six species ; five in species of ''[[Drosophila]]'' and one in the family ''[[Muscidae]]''.<ref name="Longdon et al 2010">{{cite journal | last1 = Longdon | first1 = B | last2 = Obbard | first2 = DJ | last3 = Jiggins | first3 = FM | year = 2010 | title = Sigma viruses from three species of Drosophila form a major new clade in the rhabdovirus phylogeny | url= | journal = Proceedings of the Royal Society B | volume = 277 | issue = 1698| pages = 35–44 |doi = 10.1098/rspb.2009.1472 | pmid = 19812076 | pmc = 2842628 }}</ref><ref>{{cite journal | last1 = Longdon | first1 = B | last2 = Wilfert | first2 = L | last3 = Osei-Poku | first3 = J | last4 = Cagney | first4 = H | last5 = Obbard | first5 = DJ | last6 = Jiggins | first6 = FM | year = 2011 | title = Host-switching by a vertically transmitted rhabdovirus in Drosophila | url = http://rsbl.royalsocietypublishing.org/content/7/5/747.full.pdf+html | journal = Biology Letters | volume = 7 | issue = 5| pages = 747–750 | doi=10.1098/rsbl.2011.0160 | pmid=21450721 | pmc=3169049}}</ref>
==Transmission==
DMelSV, DAffSV and DObsSV are transmitted vertically by both drosophila parents (i.e. through both eggs and sperm) suggesting sigmaviruses may be a clade of vertically transmitted viruses.<ref name="Brun">Brun, G. and N. Plus (1980). The viruses of Drosophila. The genetics and biology of Drosophila. M. Ashburner and T. R. F. Wright. New York, Academic Press: 625-702.</ref><ref>{{cite journal | last1 = Longdon | first1 = B | last2 = Wilfert | first2 = L | last3 = Obbard | first3 = DJ | last4 = Jiggins | first4 = FM | year = 2011 | title = Rhabdoviruses in two species of Drosophila: vertical transmission and a recent sweep | url = http://www.genetics.org/content/188/1/141.full?sid=65d3e1f3-9b9e-4129-8c0f-d334bfdafc6c | journal = Genetics | volume = 188 | issue = 1| pages = 141–150 | doi=10.1534/genetics.111.127696 | pmid=21339477 | pmc=3120147}}</ref> This unusual mode of biparental vertical transmission allows the virus to spread through host populations even if it reduces the fitness of infected hosts.<ref>{{cite book | last1 = L'Heritier | first1 = PH | year = 1970 | chapter = Drosophila viruses and their role as evolutionary factors | title = Evolutionary Biology | volume = 4 | pages = 185–209 | publisher = Appleton-Century-Crofts | isbn = 978-0-390-27033-7 }}</ref>
==Host resistance==
In ''[[Drosophila melanogaster]]'' resistance alleles in the genes ''ref(2)p'' and ''CHKov 1 and 2'' and  have been identified that explain a large amount of the genetic variation in susceptibility to DMelSV infection.<ref>{{cite journal | last1 = Wayne | first1 = M L | last2 = Contamine | first2 = D | last3 = Kreitman | first3 = M | year = 1996 | title = Molecular population genetics of ref(2)P, a locus which confers viral resistance in Drosophila | journal = Mol Biol Evol | volume = 13 | issue = 1| pages = 191–199 | doi=10.1093/oxfordjournals.molbev.a025555| pmid = 8583891 | doi-access = free }}</ref><ref>{{cite journal | last1 = Bangham | first1 = J | last2 = Obbard | first2 = DJ | last3 = Kim | first3 = KW | last4 = Haddrill | first4 = PR | last5 = Jiggins | first5 = FM | year = 2007 | title = The age and evolution of an antiviral resistance mutation in Drosophila melanogaster | url= | journal = Proceedings of the Royal Society B | volume = 274 | issue = 1621| pages = 2027–2034 | doi=10.1098/rspb.2007.0611 | pmid=17550883 | pmc=1914336}}</ref><ref>{{cite journal | last1 = Magwire | first1 = MM | last2 = Bayer | first2 = F | last3 = Webster | first3 = CL | last4 = Cao | first4 = C | last5 = Jiggins | first5 = FM | year = 2011 | title = Successive Increases in the Resistance of Drosophila to Viral Infection through a Transposon Insertion Followed by a Duplication | doi = 10.1371/journal.pgen.1002337|pmc=3197678  | journal = PLOS Genet | volume = 7 | issue = 10| page = e1002337 | pmid = 22028673 | doi-access = free }}</ref>
==Structure==
Sigmavirions are enveloped, with bullet shaped geometries. Sigmavirus genomes are linear, around 12.6 kb in length. The genome codes for 6 proteins (3' to 5': N-P-X-M-G-L).<ref name="Longdon et al 2010"/><ref name="Brun"/>
{| class="wikitable sortable" style="text-align:center"
|-
! Genus !! Structure || Symmetry !! Capsid !! Genomic arrangement !! Genomic segmentation
|-
|''Sigmavirus''||Bullet-shaped||||Enveloped||Linear||
|}
==Life cycle==
Viral replication is cytoplasmic. Entry into the host cell is achieved by attachment of the viral G glycoproteins to host receptors, which mediates clathrin-mediated endocytosis. Replication follows the negative stranded RNA virus replication model. Negative stranded RNA virus transcription, using polymerase stuttering is the method of transcription. The virus exits the host cell by budding, and  tubule-guided viral movement. Drosophilae serve as the natural host.<ref name=ViralZone/>
{| class="wikitable sortable" style="text-align:center"
|-
! Genus !! Host details !! Tissue tropism !! Entry details !! Release details !! Replication site !! Assembly site !! Transmission
|-
|''Sigmavirus''||''Drosophila''||None||Clathrin-mediated endocytosis||Budding||Cytoplasm||Cytoplasm||Unknown
|}
==References==
{{Reflist}}
==External links==
* [http://viralzone.expasy.org/all_by_species/4656.html '''Viralzone''': Sigmavirus]
* [http://ictvonline.org/virusTaxonomy.asp '''ICTV''']
{{Baltimore classification}}
{{Taxonbar|from=Q7512418}}
[[Category:Rhabdoviridae]]
[[Category:Virus genera]]