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Members of the genus Betapartitivirus infect plants and fungi. Betapartitiviruses have two dsRNA segments that are believed to be individually encapsidated in separate particles, and genomes typically ranging from 4.3–4.8 kbp in total.
Based on negative-contrast electron microscopy, the virions of white clover cryptic virus 2 are isometric and approximately 38 nm in diameter (Boccardo et al., 1985). The particles appear rounded and are not penetrated by stain (Figure 1.Betapartitivirus). The structure of Fusarium poae virus 1 has been determined by electron cryomicroscopy and 3D reconstruction (Tang et al., 2010). The outer diameter of the capsid is about 40 nm, and each particle contains 120 CP molecules arranged with icosahedral symmetry (Tang et al., 2010). Other reported betapartitivirus particle sizes range from 25 to 35 nm in diameter (Strauss et al., 2000, Lim et al., 2005, Sasaki et al., 2005, Li et al., 2009, Ziegler et al., 2012).
Figure 1.Betapartitivirus. Negative-contrast electron micrograph of particles of an isolate of White clover cryptic virus 2. The bar represents 50 nm. (Ghabrial et al., 2000).
Virion buoyant density of white clover cryptic virus 2 in CsCl is 1.375 g cm−3 (Boccardo et al., 1985).
Viral genome comprises two dsRNA segments, which are each about 2.1–2.4 kbp.
There is a single major coat protein (CP) with predicted Mr of 71–77 kDa. The predicted Mr of the RNA-dependent RNA polymerase (RdRP), as deduced from nucleotide sequence analysis, ranges from 77 to 87 kDa. Virion-associated RNA polymerase activity is present.
Each genome segment is monocistronic: the larger genome segment typically encodes the RdRP and the smaller one encodes the putative CP. Atkinsonella hypoxylon virus has a third dsRNA segment appearing not to encode any proteins (see GenBank record L39127) (Oh and Hillman 1995). Members of genus Betapartitivirus commonly have poly(A) tracts (≥10 nt) near to the coding-strand 3ʹ-terminus of one or both genome segments.
Members of the genus Betapartitivirus infect ascomycetous and basidiomycetous fungi (ten species) and plants (seven species). They are transmitted intracellularly during cell division (plants, fungi) or cell fusion and sporogenesis (fungi). Plant betapartitiviruses include former members of the defunct genus Betacryptovirus, which are associated with persistent infections (Lesker et al., 2013). Various host effects have been described for fungal betapartitiviruses: Rosellinia necatrix virus 1 mediates changes in host colony morphology and decreased dispersal via conidiospores (Kanematsu et al., 2010), and the related, unclassified Sclerotinia sclerotiorum partitivirus 1 reduces the virulence of its host (Xiao et al., 2014).
The species demarcation criteria within genus Betapartitivirus are:
SpeciesVirus name(s)Exemplar isolateExemplar accession numberExemplar RefSeq numberAvailable sequenceOther isolatesOther isolate accession numbersVirus abbreviationIsolate abbreviationAtkinsonella hypoxylon virusAtkinsonella hypoxylon virus2HRNA1: L39125; RNA2: L39126RNA1: NC_003470; RNA2: NC_003471Complete genomeAhVCannabis cryptic virusCannabis cryptic virusFedora17RNA1: JN196536; RNA2: JN196537Complete genomeCCVCannabis cryptic virusCannabis cryptic virushemp09RNA1: KX709964; RNA2: KX709965CCVCeratocystis resinifera virus 1Ceratocystis resinifera virus 1Deng RNA1: AY603052; RNA2: AY603051RNA1: NC_010755; RNA2: NC_010754Complete genomeCrV1Ceratocystis resinifera virus 1Ceratocystis polonica partitivirusCMW7151RNA1: AY247204; RNA2: AY247205CpPVCeratocystis resinifera virus 1Ceratocystis polonica partitivirusCMW2284RNA1: AY260756; RNA2: AY260757CpPVCrimson clover cryptic virus 2crimson clover cryptic virus 2IPP/IncarnatSKRNA1: JX971982; RNA2: JX971983Complete genomeCCCV2Dill cryptic virus 2dill cryptic virus 2IPP/hortorumRNA1: JX971984; RNA2: JX971985RNA1: NC_021147; RNA2: NC_021148Complete genomeDCV2Fusarium poae virus 1Fusarium poae virus 1A11RNA1: AF047013; RNA2: AF015924RNA1: NC_003884; RNA2: NC_003883Complete genomeFpV1Fusarium poae virus 1Fusarium poae virus 1240374RNA1: LC150606; RNA2: LC150607FpV1Heterobasidion partitivirus 2Heterobasidion partitivirus 2pa1 RNA1: HM565953; RNA2: HM565954Complete genomeHetRV2Heterobasidion partitivirus 2Heterobasidion partitivirus 2pa1/b RNA1: KF551880HetRV2Heterobasidion partitivirus 2Heterobasidion partitivirus 2pa1/c RNA1: KF551881HetRV2Heterobasidion partitivirus 2Heterobasidion partitivirus 2pa1/e RNA1: KF551882HetRV2Heterobasidion partitivirus 2Heterobasidion partitivirus 2pa1/f RNA1: KF551883HetRV2Heterobasidion partitivirus 2Heterobasidion partitivirus 2pa1/d RNA1: KF551884HetRV2Heterobasidion partitivirus 2Heterobasidion partitivirus 2pa1/g RNA1: KF551885HetRV2Heterobasidion partitivirus 7Heterobasidion partitivirus 7pa1 RNA1: JN606091; RNA2: JN606090Complete genomeHetRV7Heterobasidion partitivirus 7Heterobasidion partitivirus 7pa1/b RNA1: KF551886HetRV7Heterobasidion partitivirus 7Heterobasidion partitivirus 7pa1/c RNA1: KF551887HetRV7Heterobasidion partitivirus 8Heterobasidion partitivirus 8ir1 RNA1: JX625227; RNA2: JX625228Complete genomeHetRV8Heterobasidion partitivirus PHeterobasidion partitivirus PIhrmarkRNA1: AF473549Partial genomeHetPVPHop trefoil cryptic virus 2hop trefoil cryptic virus 2IPP/GelbSKRNA1: JX971980; RNA2: JX971981RNA1: NC_021098; RNA2: NC_021099Complete genomeHTCV2Pleurotus ostreatus virus 1Pleurotus ostreatus virus 1South KoreaRNA1: AY533038; RNA2: AY533036RNA1: NC_006961; RNA2: NC_006960Complete genomePoV1Primula malacoides virus 1Primula malacoides virus 1ChinaRNA1: EU195326; RNA2: EU195327RNA1: NC_013109; RNA2: NC_013110Complete genomePmV1Red clover cryptic virus 2red clover cryptic virus 2IPP/NemaroRNA1: JX971978; RNA2: JX971979RNA1: NC_021096; RNA2: NC_021097Complete genomeRCCV2Rhizoctonia solani virus 717Rhizoctonia solani virus 717717RNA1: AF133290; RNA2: AF133291RNA1: NC_003801; RNA2: NC_003802Complete genomeRsVRosellinia necatrix virus 1Rosellinia necatrix virus 1ayamaRNA1: AB113347; RNA2: AB113348RNA1: NC_007537; RNA2: NC_007538Complete genomeRnV1White clover cryptic virus 2white clover cryptic virus 2GermanyRNA1: JX971976; RNA2: JX971977RNA1: NC_021094; RNA2: NC_021095Complete genomeWCCV2
Fusarium poae partitivirus 2
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