ARS | Publication request: Spissistilus festinus reovirus: a novel, unassigned species of the family Reoviridae infecting the three-cornered alfalfa hopper

Submitted to: American Society for Virology Meeting
Publication Type: Abstract Only
Publication Acceptance Date: February 1, 2011
Publication Date: June 1, 2011
Citation: Spear, A., Sisterson, M.S., Stenger, D.C. 2011. Spissistilus festinus reovirus: a novel, unassigned species of the family Reoviridae infecting the three-cornered alfalfa hopper [abstract]. American Society for Virology Meeting. p.334.

Technical Abstract: A complex set of double stranded RNAs (dsRNA) were isolated from threecornered alfalfa hopper (Spissistilus festinus), a plant-feeding hemipteran insect pest. A subset of these dsRNAs constitute the genome of a novel, unassigned reovirus designated as Spissistilus festinus reovirus (SpFRV). Phylogenetic analysis of the RNA directed RNA polymerase (RdRp) showed SpFRV to be most closely related to the unclassified reovirus Raspberry latent virus (RpLV) and Rice ragged stunt virus (RRSV; genus Oryzavirus) at 29.6% and 27.6% amino acid identity, respectively. SpFRV also encodes a protein homologous to RRSV Pns7, containing two NTP binding motifs conserved among turreted reoviruses, placing SpFRV within the subfamily Spinareovirinae. RdRp phylogeny also grouped SpFRV with turreted reoviruses. Although two additional SpFRV genomic RNAs encode structural proteins homologous to those of the RRSV major capsid protein and structural protein P4, proteins encoded by four additional SpFRV genomic segments used as queries in BLASTp searches failed to return subjects with significant e values. Among eight SpFRV genome segments for which sequences have been determined, all share conserved terminal sequences at the 5’-end (AGAGA) and 3’-end (CGAUGUUGU) of the positive sense strand that are distinct from all sequenced species of the family Reoviridae. Sequences flanking conserved termini of each segment were complementary, typical of the family Reoviridae. Collectively, the low level of sequence identity with other reoviruses and distinct terminal sequences suggest that SpFRV may be considered the type species of a new genus of Reoviridae within the subfamily Spinareovirinae. Alternatively, SpFRV and RpLV could be included in the genus Oryzavirus, but to do so would group species with limited sequence identity and different segment termini, and SpFRV has not been demonstrated to infect plants. Surveys indicated SpFRV was present in threecornered alfalfa hopper populations in the Southern San Joaquin Valley of California, with incidence ranging from 10% to 60% in 23 of 24 sample sets analyzed.