Genus: Poacevirus


Genus: Poacevirus

Distinguishing features

Triticum mosaic virus (TriMV) is transmitted by the wheat curl mite and has an unusually long 5´-untranslated region. Vectors are unknown for the other members of the genus.

Virion

Morphology

Virions of sugarcane streak mosaic virus (SCSMV) are flexuous filaments 890 nm×15 nm in size.

Nucleic acid

Virions contain a positive-sense ssRNA of 9.7–10.2 kb with a 3′-poly(A) terminus.

Proteins

The TriMV coat (capsid) protein (CP) is a single peptide of 293 aa with a MW of about 32 kDa. For SCSMV the viral CP is 281 aa with the MW estimated to be 36 kDa. Caladenia virus A (CalVA) has a CP of 285 aa and MW of 31

Genome organization and replication

The TriMV genome consists of 10,266 nt. The genome encodes a polyprotein of 3,122 aa. TriMV has an unusually long 5´-untranslated region, but this is not shared by members of the other two species. The order of coding regions is typical of that of the potyviruses (Figure 2.Potyviridae). Most known potyvirus motifs are present in the polyprotein of poaceviruses.  The aphid transmission amino acid sequence motifs present in the HC-Pros (KITC, PTK) and CPs (DAG) of potyviruses are absent in poaceviruses. The zinc-finger-like motif H-(X2)-C-(X29)-C-(X2)-C in the tritimovirus wheat streak mosaic virus (WSMV) HC-Pro is essential for its transmission by mites. A similar motif in the poacevirus CalVA (unknown vector) is present  as H-(X2)-H-(X29)-C-(X2)-C (Wylie et al., 2012). In TriMV (mite transmitted) and SCSMV (unknown vector), the C-(X2)-C motif exists, but the remainder of the motif is incomplete. P1 rather than the HC-Pro suppresses the host RNA-suppression response in TriMV (Tatineni et al., 2012). Members of the genus Poacevirus are phylogenetically closest to those of another mite-transmitted genus, Tritimovirus.

Antigenicity

A Western blot revealed that antiserum raised to SCSMV weakly cross-reacts with wheat streak mosaic virus capsid protein. SCSMV does not cross react with other sugarcane-infecting members of the Potyviridae.

Biology

Host range

TriMV and SCSMV only infect hosts in the Gramineae, while CalVA infects orchids (Wylie et al., 2012).

Transmission

TriMV is transmitted by the wheat curl mite (Aceria tosichella).

Species demarcation criteria

See discussion under family description.

Member species

SpeciesVirus name(s)Exemplar isolateExemplar accession numberExemplar RefSeq numberAvailable sequenceOther isolatesOther isolate accession numbersVirus abbreviationIsolate abbreviation
Caladenia virus ACaladenia virus AKP1JX156425NC_018572Complete genomeCalVA
Sugarcane streak mosaic virussugarcane streak mosaic virusPAKGQ388116NC_014037Complete genomeSCSMV
Triticum mosaic virusTriticum mosaic virusU06-123FJ263671NC_012799Complete genomeTriMV

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

Derivation of names

Poacevirus: from Poaceae, the family name of the hosts of members of two species in the genus.