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. The vectors are currently 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 9.7–10.2 kb in size with a 3′-poly(A) terminus.

Proteins

The TriMV CP is a single peptide of 293 aa, and its MW is 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 3122 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 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 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. The 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 WSMV protein. SCSMV did not cross react with other sugarcane-infecting members of the Potyviridae.

Biology

Host range

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

Transmission

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

Derivation of names

Poace: from Poaceae, the family name of the hosts of two member species.

 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.
Download GenBank/EMBL query for sequences listed in the table here.