Distinguishing features
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.
Virion
Morphology
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). |
Physicochemical and physical properties
Virion buoyant density of white clover cryptic virus 2 in CsCl is 1.375 g cm−3 (Boccardo et al., 1985).
Nucleic acid
Viral genome comprises two dsRNA segments, which are each about 2.1–2.4 kbp.
Proteins
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.
Genome organization and replication
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 3′-terminus of one or both genome segments.
Biology
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).
Species demarcation criteria
The species demarcation criteria within genus Betapartitivirus are:
- ≤ 90% aa sequence identity in the RdRP, and
- ≤ 80% aa sequence identity in the CP
Member species
Species | Virus name | Isolate | Accession number | RefSeq number | Available sequence | Virus Abbrev. | |
---|---|---|---|---|---|---|---|
Atkinsonella hypoxylon virus | Atkinsonella hypoxylon virus | 2H | RNA1: L39125; RNA2: L39126 All | RNA1: NC_003470; RNA2: NC_003471 All | Complete genome | AhV | |
Cannabis cryptic virus | Cannabis cryptic virus | Fedora17 | RNA1: JN196536; RNA2: JN196537 All | Complete genome | CCV | ||
Cannabis cryptic virus | Cannabis cryptic virus | hemp09 | RNA1: KX709964; RNA2: KX709965 All | Complete genome | CCV | ||
Ceratocystis resinifera virus 1 | Ceratocystis resinifera virus 1 | Deng | RNA1: AY603052; RNA2: AY603051 All | RNA1: NC_010755; RNA2: NC_010754 All | Complete genome | CrV1 | |
Ceratocystis resinifera virus 1 | Ceratocystis polonica partitivirus | CMW7151 | RNA1: AY247204; RNA2: AY247205 All | Complete genome | CpPV | ||
Ceratocystis resinifera virus 1 | Ceratocystis polonica partitivirus | CMW2284 | RNA1: AY260756; RNA2: AY260757 All | Complete genome | CpPV | ||
Crimson clover cryptic virus 2 | crimson clover cryptic virus 2 | IPP_IncarnatSK | RNA1: JX971982; RNA2: JX971983 All | RNA1: NC_038837; RNA2: NC_038838 All | Complete genome | CCCV2 | |
Dill cryptic virus 2 | dill cryptic virus 2 | IPP_hortorum | RNA1: JX971984; RNA2: JX971985 All | RNA1: NC_021147; RNA2: NC_021148 All | Complete genome | DCV2 | |
Fusarium poae virus 1 | Fusarium poae virus 1 | A11 | RNA1: AF047013; RNA2: AF015924 All | RNA1: NC_003884; RNA2: NC_003883 All | Complete genome | FpV1 | |
Fusarium poae virus 1 | Fusarium poae virus 1 | 240374 | RNA1: LC150606; RNA2: LC150607 All | Complete genome | FpV1 | ||
Heterobasidion partitivirus 2 | Heterobasidion partitivirus 2 | pa1 | RNA1: HM565953; RNA2: HM565954 All | RNA1: NC_038839; RNA2: NC_038840 All | Complete genome | HetRV2 | |
Heterobasidion partitivirus 2 | Heterobasidion partitivirus 2 | pa1-b | RNA1: KF551880 | Partial genome | HetRV2 | ||
Heterobasidion partitivirus 2 | Heterobasidion partitivirus 2 | pa1-c | RNA1: KF551881 | Partial genome | HetRV2 | ||
Heterobasidion partitivirus 2 | Heterobasidion partitivirus 2 | pa1-e | RNA1: KF551882 | Partial genome | HetRV2 | ||
Heterobasidion partitivirus 2 | Heterobasidion partitivirus 2 | pa1-f | RNA1: KF551883 | Partial genome | HetRV2 | ||
Heterobasidion partitivirus 2 | Heterobasidion partitivirus 2 | pa1-d | RNA1: KF551884 | Partial genome | HetRV2 | ||
Heterobasidion partitivirus 2 | Heterobasidion partitivirus 2 | pa1-g | RNA1: KF551885 | Partial genome | HetRV2 | ||
Heterobasidion partitivirus 7 | Heterobasidion partitivirus 7 | pa1-a | RNA1: JN606091; RNA2: JN606090 All | RNA1: NC_035485; RNA2: NC_035486 All | Complete genome | HetRV7 | |
Heterobasidion partitivirus 7 | Heterobasidion partitivirus 7 | pa1-b | RNA1: KF551886 | Partial genome | HetRV7 | ||
Heterobasidion partitivirus 7 | Heterobasidion partitivirus 7 | pa1-c | RNA1: KF551887 | Partial genome | HetRV7 | ||
Heterobasidion partitivirus 8 | Heterobasidion partitivirus 8 | ir1 | RNA1: JX625227; RNA2: JX625228 All | RNA1: NC_038841; RNA2: NC_038842 All | Complete genome | HetRV8 | |
Heterobasidion partitivirus P | Heterobasidion partitivirus P | Ihrmark | RNA1: AF473549 | RNA1: NC_043393 | Partial genome | HetPVP | |
Hop trefoil cryptic virus 2 | hop trefoil cryptic virus 2 | IPP_GelbSK | RNA1: JX971980; RNA2: JX971981 All | RNA1: NC_021098; RNA2: NC_021099 All | Complete genome | HTCV2 | |
Pleurotus ostreatus virus 1 | Pleurotus ostreatus virus 1 | South Korea | RNA1: AY533038; RNA2: AY533036 All | RNA1: NC_006961; RNA2: NC_006960 All | Complete genome | PoV1 | |
Primula malacoides virus 1 | Primula malacoides virus 1 | China | RNA1: EU195326; RNA2: EU195327 All | RNA1: NC_013109; RNA2: NC_013110 All | Complete genome | PmV1 | |
Red clover cryptic virus 2 | red clover cryptic virus 2 | IPP_Nemaro | RNA1: JX971978; RNA2: JX971979 All | RNA1: NC_021096; RNA2: NC_021097 All | Complete genome | RCCV2 | |
Rhizoctonia solani virus 717 | Rhizoctonia solani virus 717 | 717 | RNA1: AF133290; RNA2: AF133291 All | RNA1: NC_003801; RNA2: NC_003802 All | Complete genome | RsV | |
Rosellinia necatrix virus 1 | Rosellinia necatrix virus 1 | Okayama | RNA1: AB113347; RNA2: AB113348 All | RNA1: NC_007537; RNA2: NC_007538 All | Complete genome | RnV1 | |
White clover cryptic virus 2 | white clover cryptic virus 2 | IPP_Lirepa | RNA1: JX971976; RNA2: JX971977 All | RNA1: NC_021094; RNA2: NC_021095 All | Complete genome | WCCV2 |
Virus names, the choice of exemplar isolates, and virus abbreviations, are not official ICTV designations.
Related, unclassified viruses
Virus name* |
Accession number |
|
dsRNA1/RdRP |
dsRNA2/CP |
|
Sclerotinia sclerotiorum partitivirus 1 strain SsPV1-WF-1 | ||
Ustilaginoidea virens partitivirus 3 strain HP-30 | ||
Rosellinia necatrix partititivirus 6 strain W113 | ||
Fusarium poae partitivirus 2 |