Family: Bromoviridae

Genus: Anulavirus

Distinguishing features 

RNA3 is slightly larger than RNA2, unlike other members of this family. The 2a protein is the smallest reported for viruses in the family (78.9 kDa).

Virion

Morphology

Virus particles are quasi-spherical, with a diameter ranging from 25 to 35 nm, and have a poorly resolved surface structure.

Physicochemical and physical properties

In sucrose density gradients, virions sediment as three components of 80 (TV, top), 90 (MV, middle) and 118 S (BV, bottom). In analytical centrifugation virions have single buoyant densities at equilibrium of 1.35 g cm⁻³ in CsCl or 1.29 g cm⁻³ in Cs₂SO_4.

Nucleic acid

The genome of the tomato isolate of pelargonium zonate spot virus (PZSV) comprises 8477 nucleotides distributed among three linear, positive-sense ssRNAs that encode four proteins, denoted 1a, 2a, 3a (movement protein, MP) and CP (coat protein) (Finetti-Sialer and Gallitelli 2003).

Proteins

Virions contain a single CP of 23 kDa.

Genome organization and replication

The genome is organized as depicted in Figure 2B.Bromoviridae. Coat protein is not required for activation of the genome.

Biology

Isolates of Pelargonium zonate spot virus infect tomato and artichoke and are common in weeds (e.g. Diplotaxis erucoides where it is also seed-borne). The virus is in/on pollen that is carried on the bodies of thrips feeding on susceptible hosts. An Israeli strain of PZSV is vertically-transmissible via both pollen and seeds in tomato plants (Lapidot et al., 2010). Infected cells have severe cytopathological alterations. Amazon lily mild mottle virus (ALiMMV) has been found only in Amazon lily (Eucharis grandiflora) whereas the unclassified virus cassava Ivorian bacilliform virus (CIBV) has been detected only in cassava (Manihot esculenta). Both CIBV and ALiMMV are mechanically transmissible and have a narrow experimental host range.

Antigenicity

Virions are weak immunogens and must be fixed before injection into rabbits to raise antibodies. An in vitro-synthesized fusion protein has been used to raise an antiserum against pelargonium zonate spot virus (PZSV) that was proven to be highly specific and sensitive in western blot and ELISA tests (Gulati-Sakhuja et al., 2009).

Species demarcation criteria

PZSV, ALiMMV and grapevine line pattern virus (GLPV), members of the species Pelargonium zonate spot virus, Amazon lily mild mottle virus and Anulavirus GLPV, respectively, are distinguished by differences in experimental host range and genome sequence (Fuji et al., 2013, Elbeaino et al., 2020). The genomes of PZSV and ALiMMV are 53% identical, while the amino acid sequences of their 1a, 2a, 3a and CP proteins are 44.4%, 50.4%, 47.1% and 34.0% identical, respectively. 

Related, unclassified viruses

Virus names and virus abbreviations are not official ICTV designations.