Genus: Alphachrysovirus


Genus: Alphachrysovirus

Distinguishing features

Members of the genus Alphachrysovirus infect ascomycetous fungi and have been found associated with plants and insects.

Virion

Nucleic acid

Members have three or four dsRNA genome segments ranging from 2.5 to 3.7 kbp, as exemplified by Penicillium chrysogenum virus (PcV) (Figure 2.Chrysoviridae), whose segments are 2.9–3.6 kbp (Table 1.Alphachrysovirus) (Jiang and Ghabrial 2004). The genome comprises 8.9–13.1 kbp in total. The dsRNA segments are individually encapsidated in separate particles.

Proteins

Virion proteins include P1, which has RNA-directed RNA polymerase (RdRP) and NTPase activity, and the capsid protein (CP), usually P2.

Genome organization and replication

Protein database searches reveal that PcV-P3 sequence shares a “phytoreo S7 domain” with a protein family consisting of several phytoreovirus P7 proteins that are known to be virus core proteins (Jiang and Ghabrial 2004, Liu et al., 2012). Interestingly, the N-terminal regions of PcV-P3 (and the corresponding alphachryso-P3 proteins of other alphachrysoviruses) share significant sequence similarity with comparable N-terminal regions of the RNA-directed RNA polymerase (RdRP) encoded by dsRNA1 of alphachrysoviruses (Jiang and Ghabrial 2004, Liu et al., 2012). Furthermore, HHPred (Soding et al., 2005) predicts a separate P-loop NTPase domain near the N terminus of alphachryso-P1, which overlaps the region of alphachryso-P1 that is represented by homologous sequences in alphachryso-P3. The P7/P-loop NTPase domain (Pathak et al., 2014) in alphachryso-P1 is independent (non-overlapping) of the RdRP domain in alphachryso-P1. Thus, alphachryso-P1 has at least two distinct enzymatic activities, RdRP and NTPase, mediated by at least two different domains. The PcV-P4 (and comparable proteins of other alphachrysoviruses) contains the motifs that form the conserved core of the ovarian tumour gene-like superfamily of predicted cysteine proteases (Covelli et al., 2004). HHPred also shows that alphachryso-P4 has a region of homology with alphachryso-P2/capsid protein. All of these motifs/homologies are shared by all alphachrysoviruses with quadripartite genomes (quadrichrysoviruses). Trichrysoviruses, which mostly infect plants, lack a PcV-P3 homolog; otherwise the virus-encoded proteins share the same motifs in the same relative positions as in the homologous proteins of fungal chrysoviruses with quadripartite genomes.

Table 1.Alphachrysovirus. Genome content and encoded proteins of Penicillium chrysogenum virus (PcV)

Segment

bpa

Mass of encoded protein in Dab

Designation and function of encoded protein

dsRNA1

3,562

128,548 (1,117 aa)

P1, RdRP

dsRNA2

3,200

108,806 (982 aa)

P2, CP

dsRNA3

2,976

101,458 (912 aa)

Alphachryso-P3, unknown

dsRNA4

2,902

94,900 (847 aa)

Alphachryso-P4, unknown

a Deduced from sequence of full-length cDNA clones
b Predicted from aa sequence encoded by full-length cDNA; the numbers of aa residues is given in parentheses.

Biology

Trichrysoviruses are mostly plant viruses (Figure 3.Chrysoviridae), (Zhang et al., 2017, Li et al., 2013, Zhong et al., 2016). More specifically, four of the five known trichrysoviruses infect plants. Only Colletotrichum gloeosporioides chrysovirus 1 (CgCV1) infects a plant pathogenic fungus (Zhang et al., 2017). Interestingly, CgCV1clusters with the fungal quadrichrysoviruses, but not with the plant trichrysoviruses.

Species demarcation criteria

Species demarcation criteria:

  • Host of isolation
  • Nucleotide and deduced amino acid sequence data (≤ 70% and ≤ 53% aa sequence identity in the RdRP and CP, respectively)
  • length of dsRNA genome segments
  • length of 5′-UTR

Species demarcation considers a combination of each of the criteria listed above. While nucleotide and amino acid sequence relatedness are important criteria for species demarcation, the other listed criteria may be useful in the demarcation of genetically closely related viruses that nevertheless belong to different species.

Member species

Exemplar isolate of the species
SpeciesVirus nameIsolateAccession numberRefSeq numberAvailable sequenceVirus Abbrev.
Amasya cherry disease associated chrysovirusAmasya cherry disease associated chrysovirusTurkeydsRNA1: AJ781166; dsRNA2: AJ781165; dsRNA3: AJ781164; dsRNA4: AJ781163dsRNA1: NC_009947; dsRNA2: NC_009946; dsRNA3: NC_009945; dsRNA4: NC_009944Complete genomeACDACV
Amasya cherry disease associated chrysoviruscherry chlorotic rusty spot associated chrysovirusItalydsRNA1: AJ781397; dsRNA2: AJ781398; dsRNA3: AJ781399; dsRNA4: AJ781400Complete genomeCCRSACV
Anthurium mosaic-associated chrysovirusAnthurium mosaic-associated virusPHAdsRNA1: FJ899675; dsRNA2: FJ899676; dsRNA3: FJ899677dsRNA1: NC_043676; dsRNA2: NC_043677; dsRNA3: NC_043678Complete genomeAMAV
Aspergillus fumigatus chrysovirusAspergillus fumigatus chrysovirusA56dsRNA1: FN178512; dsRNA2: FN178513; dsRNA3: FN178514; dsRNA4: FN178515dsRNA1: NC_038872; dsRNA2: NC_038873; dsRNA3: NC_038871; dsRNA4: NC_038874Complete genomeAfCV
Brassica campestris chrysovirusBrassica campestris chrysovirus 1HubeidsRNA1: KP782031; dsRNA2: KP782030; dsRNA3: KP782029dsRNA1: NC_043660; dsRNA2: NC_043659; dsRNA3: NC_043661Complete genomeBcCV1
Colletotrichum gloeosporioides chrysovirusColletotrichum gloeosporioides chrysovirus 1HZ-1dsRNA1: KT581957; dsRNA2: KT581958; dsRNA3: KT581959dsRNA1: NC_043666; dsRNA2: NC_043668; dsRNA3: NC_043667Complete genomeCgCV1
Cryphonectria nitschkei chrysovirus 1Cryphonectria nitschkei chrysovirus 1BS122dsRNA1: GQ290649; dsRNA2: GQ290645; dsRNA3: HM013825; dsRNA4: HM013826dsRNA1: NC_038778; dsRNA2: NC_038779; dsRNA3: NC_038781; dsRNA4: NC_038780Complete coding genomeCnCV1
Fusarium oxysporum chrysovirus 1Fusarium oxysporum chrysovirus 1SharzeidsRNA1: EF152346; dsRNA2: EF152347; dsRNA3: EF152348dsRNA1: NC_043218; dsRNA2: NC_043219; dsRNA3: NC_043220partial genomeFoCV1
Helminthosporium victoriae virus 145SHelminthosporium victoriae virus 145SA9dsRNA1: AF297176; dsRNA2: AF297177; dsRNA3: AF297178; dsRNA4: AF297179dsRNA1: NC_005978; dsRNA2: NC_005979; dsRNA3: NC_005980; dsRNA4: NC_005981Complete genomeHvV145S-A9
Helminthosporium victoriae virus 145SBipolaris maydis chrysovirus 1SS01dsRNA1: KY489954; dsRNA2: KY489955; dsRNA3: KY489956; dsRNA4: KY489957Complete genomeBmCV1
Isaria javanica chrysovirusIsaria javanica chrysovirus 1IjCV-1dsRNA1: KX898416; dsRNA2: KX898417; dsRNA3: KX898418; dsRNA4: KX898419dsRNA1: NC_033277; dsRNA2: NC_033317; dsRNA3: NC_033318; dsRNA4: NC_033278Complete genomeIjCV1
Macrophomina phaseolina chrysovirusMacrophomina phaseolina chrysovirus 1TN263dsRNA1: KP900886; dsRNA2: KP900887; dsRNA3: KP900888; dsRNA4: KP900889dsRNA1: NC_043662; dsRNA2: NC_043664; dsRNA3: NC_043663; dsRNA4: NC_043665Complete genomeMpCV1
Penicillium brevicompactum virusPenicillium brevicompactum virusIndianaNo entry in GenbankPbcV
Penicillium chrysogenum virusPenicillium chrysogenum virusATCC9480dsRNA1: AF296439; dsRNA2: AF296440; dsRNA3: AF296441; dsRNA4: AF296442dsRNA1: NC_007539; dsRNA2: NC_007540; dsRNA3: NC_007541; dsRNA4: NC_007542Complete genomePcV
Penicillium cyaneofulvum virusPenicillium cyaneo-fulvum virusIMI58138No entry in GenbankPcfV
Persea americana chrysovirusPersea americana chrysovirusSpaindsRNA1: KJ418374; dsRNA2: KJ418375; dsRNA3: KJ418376dsRNA1: NC_043506; dsRNA2: NC_043508; dsRNA3: NC_043507Complete genomePaCV
Raphanus sativus chrysovirusRaphanus sativas chrysovirus 113dsRNA1: JQ045335; dsRNA2: JQ045336; dsRNA3: JQ045337dsRNA1: NC_043657; dsRNA2: NC_043656; dsRNA3: NC_043658Complete genomeRsCV1
Shuangao insect-associated chrysovirusShuangao chryso-like virusWSB68555dsRNA1: MF176340; dsRNA2: MF176341; dsRNA3: MF176342; dsRNA4: MF176343Complete genomeSCLV
Verticillium dahliae chrysovirus 1Verticillium dahliae chrysovirus 1ChinadsRNA1: HM004067; dsRNA2: HM004068; dsRNA3: HM004069; dsRNA4: HM004070dsRNA1: NC_038784; dsRNA2: NC_038782; dsRNA3: NC_038785; dsRNA4: NC_038783Complete genomeVdCV1

Virus names, the choice of exemplar isolates, and virus abbreviations, are not official ICTV designations.