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Toufic Elbeaino, Michele Digiaro, Nicole Mielke-Ehret, Hans-Peter Muehlbach and Giovanni P. Martelli
Edited by F. Murilo Zerbini and Sead Sabanadzovic
A summary of this ICTV Report chapter has been published as an ICTV Virus Taxonomy Profile article in the Journal of General Virology, and should be cited when referencing this online chapter as follows:
Elbeaino, T., Digiaro, M., Mielke-Ehret, N., Muehlbach, H., Martelli, G.P., and ICTV Report Consortium, 2018, ICTV Virus Taxonomy Profile: Fimoviridae, Journal of General Virology, 99, 1478–1479
Members of the family Fimoviridae are plant viruses with segmented, linear, single-stranded, negative-sense RNA genomes that are distantly related to orthotospoviruses (family Tospoviridae) and orthobunyaviruses (family Peribunyaviridae) (Table 1.Fimoviridae). The family Fimoviridae, order Bunyavirales, includes one genus (Emaravirus) with nine species. Fimoviruses are transmitted to plants by eriophyid mite vectors and induce similar characteristic cytopathologies in their host plants, including the presence of double membrane bounded bodies (DMBs) in the cytoplasm of the virus-infected cells.
Table 1.Fimoviridae. Characteristics of members of the family Fimoviridae.
European mountain ash ringspot-associated virus, Hamburg (RNA1: AY563040; RNA2: AY563041; RNA3: DQ831831; RNA4: DQ831828 ), species European mountain ash ringspot-associated emaravirus, genus Emaravirus, family Fimoviridae, order Bunyavirales
Approximately spherical and enveloped with diameter 80–100 nm
Four to eight segments of negative-sense ssRNA (12.3–18.5 kb in total)
From capped mRNAs (produced by "cap snatching" from host mRNAs) which are complementary to the vRNAs
Cercis, fig, kiwi, maize, pigeonpea, raspberry, rose, Sorbus, wheat
Single genus including nine species
Fimoviruses have enveloped, approximately spherical virions, with a diameter of 80–100 nm (Figure 1.Fimoviridae), containing at least four negative-sense ssRNA segments (Elbeaino et al., 2009a).
Figure 1.Fimoviridae. Immunosorbent electron micrograph of virions of European mountain ash ringspot-associated virus. The bar represents 100 nm (Courtesy Inga Ludenberg, University of Hamburg, Germany).
The viral genome comprises four (European mountain ash ringspot-associated virus) to eight segments of negative-sense ssRNA (High Plains wheat mosaic virus,) comprising 12.3 to 18.5 kb in total. Genomic RNAs are not capped or polyadenylated and all contain complementary sequences (18–20 nt, depending on the segment) at their 5′- and 3′-termini. Five conserved motifs (A–E) in the amino acid sequence of the RNA-dependent RNA polymerase (RdRP) protein are similar to those in bunyavirales L segments (Elbeaino et al., 2009b).
Each RNA segment of the genome encodes a single protein translated from the complementary strand as follows: RNA1 - RNA-dependent RNA polymerase (RdRP, p1, 264–269 kDa; 226.9 kDa in Actinidia chlorotic ringspot-associated virus); RNA2 - a glycoprotein precursor (GP, p2, 73–76.6 kDa) that is predicted to be cleaved into products of 21.5–25.0 and 51–52 kDa; RNA3 - the nucleocapsid protein (NP, p3, 32–35.6 kDa); RNA4 - a putative movement protein (MP, p4, ca. 40.5–43.6 kDa)
Fimoviruses differ from other related viruses (orthotospoviruses and orthobunyaviruses) by having a larger number of genomic RNA segments. RNA1 to RNA4 each encode a single protein (Figure 2.Fimoviridae). The function of proteins encoded by the other RNAs (RNA5 to RNA8) remain unknown (Tatineni et al., 2014). Like other negative-sense ssRNA multipartite viruses, some fimoviruses are known to use “cap snatching” to initiate transcription and facilitate translation of their mRNAs, as it was proven in the cases of RRV and FMV (Walia and Falk 2012, Laney et al., 2011).
Figure 2.Fimoviridae. Coding strategy and genome segments of European mountain ash ringspot-associated virus (isolate Hamburg). Arrows represent the virion-complementary sense RNA, from which the proteins shown are translated. RdRP: RNA-dependent RNA polymerase; Gn and Gc: putative glycoproteins cleaved (dotted lines) from the precursor molecule; NP: nucleocapsid protein; MP: putative movement protein.
Depending on the host plant, symptoms of fimovirus infection vary from leaf mottling, blotching, vein clearing, chlorotic ringspots, yellowing, sterility of flowers to a general mosaic. Fimoviruses are transmitted by grafting and there is evidence that many have eriophyid mite vectors (Epstein and Hill 1995, Kumar et al., 2003).
Fimo: from fig mosaic
Phylogenetic trees constructed with fimovirus RdRP (Figure 3.Fimoviridae), GP or NC protein sequences display similar topologies with two (or three) main clades (Zheng et al., 2017, Elbeaino et al., 2015). The ﬁrst group includes High Plains wheat mosaic virus and raspberry leaf blotch virus, while the second comprises all the others, which in turn could be subdivided into two subgroups: i) subgroup a, comprising fig mosaic virus, rose rosette virus, pigeonpea sterility mosaic virus 2 and pigeonpea sterility mosaic virus 1, and ii) subgroup b, including European mountain ash ringspot-associated virus, redbud yellow ringspot-associated virus and Actinidia chlorotic ringspot-associated virus.
Figure 3.Fimoviridae. Phylogenetic tree constructed with amino acid sequences encoded by RNA1 (RdRP), of members of the family Fimoviridae and the orthologous L segment-encoded proteins of members of the families Peribunyaviridae and Topsoviridae. An alignment was obtained using MUSCLE within MEGA6 (Tamura et al., 2013) and a maximum likelihood tree produced with 1000 bootstrap replicates. The percentage of replicate trees in which the associated taxa clustered together in the bootstrap is shown next to the branches (when >70%). * Blackberry leaf mottle-associated virus is an unclassified virus in the family Fimoviridae. An isolate of Grapevine fanleaf virus, genus Nepovirus, family Secoviridae, was used to root the tree. This phylogenetic tree and corresponding sequence alignment are available to download from the Resources page.
Viruses of the family Fimoviridae (order Bunyavirales) are related to viruses in the families Tospoviridae and Peribunyaviridae in that they share (i) a multipartite negative-sense single-stranded RNA genome of four to eight segments; (ii) high sequence identity with orthologous proteins of members of the order Bunyavirales at equivalent genome positions in the first three RNAs (corresponding to L, M, and S RNA segments), i.e. RNA-dependent RNA polymerase (RdRP, RNA1), putative glycoprotein precursor (GP, RNA2) and putative nucleocapsid protein (NP, RNA3); (iii) five conserved motifs (A-E) in the amino acid sequence of their RdRP similar to those in L segment-encoded proteins of members of the order Bunyavirales; (iv) enveloped virions; (vi) stretches of nucleotides at both 5′- and 3′-termini of all RNA segments that are almost perfectly complementary to each other. These sequences are conserved in all genomic RNAs of fimoviruses, and are similar, but not identical, to those of other members of the order Bunyavirales.
blackberry leaf mottle-associated virus
RNA1: KY056657; RNA2: KY056658; RNA3: KY056659; RNA4: KY056660; RNA5: KY056661
Since only one genus (Emaravirus) is currently recognized in the family Firmoviridae, the family description above corresponds to the genus description. For clarity, the additional information that can be found on the genus page is also presented below.
Emara: from European mountain ash ringspot-associated virus.
Species in the genus are demarcated based upon the amino acid sequence of relevant gene products of RNA1 (RdRP), RNA2 (GP) and RNA3 (NP) differing by more than 25%.
Exemplar isolate of the speciesSpeciesVirus nameIsolateAccession numberRefSeq numberAvailable sequenceVirus Abbrev.Actinidia chlorotic ringspot-associated emaravirusActinidia chlorotic ringspot-associated virusHN-6RNA1: KT861481; RNA2: KT861482; RNA3: KT861483; RNA4: KT861484; RNA5: KT861485RNA1: NC_038769; RNA2: NC_038770; RNA3: NC_038772; RNA4: NC_038771; RNA5: NC_038773Complete genomeAcCRaVBlackberry leaf mottle associated emaravirusblackberry leaf mottle-associated virusArkansasRNA1: KY056657; RNA2: KY056658; RNA3: KY056659; RNA4: KY056660; RNA5: KY056661Complete genomeBLMaVEuropean mountain ash ringspot-associated emaravirusEuropean mountain ash ringspot-associated virusHamburgRNA1: AY563040; RNA2: AY563041; RNA3: DQ831831; RNA4: DQ831828RNA1: NC_013105; RNA2: NC_013106; RNA3: NC_013108; RNA4: NC_013107Complete genomeEMARaVFig mosaic emaravirusfig mosaic virusGr10RNA1: AM941711; RNA2: FM864225; RNA3: FM991954; RNA4: FM992851; RNA5: HE803826; RNA6: HE803827RNA1: NC_029562; RNA2: NC_029565; RNA3: NC_029563; RNA4: NC_029564; RNA5: NC_029566; RNA6: NC_029568Complete genomeFMVHigh Plains wheat mosaic emaravirusHigh Plains wheat mosaic virusNebraskaRNA1: KJ939623; RNA2: KJ939624; RNA3: KJ939626; RNA4: KJ939627; RNA5: KJ939628; RNA6: KJ939629; RNA7: KJ939630; RNA8: KJ939631RNA1: NC_029570; RNA2: NC_029549; RNA3: NC_029550; RNA4: NC_029551; RNA5: NC_029552; RNA6: NC_029553; RNA7: NC_029554; RNA8: NC_029555Complete genomeHPWMoVPigeonpea sterility mosaic emaravirus 1pigeonpea sterility mosaic virus 1IndiaRNA1: HF568801; RNA2: HF568802; RNA3: HF568803; RNA4: HF568804; RNA5: HF945448RNA1: NC_029575; RNA2: NC_029556; RNA3: NC_029574; RNA4: NC_029557; RNA5: NC_029569Complete genomePPSMV-1Pigeonpea sterility mosaic emaravirus 2pigeonpea sterility mosaic virus 2ICP8863RNA1: HF912243; RNA2: HF912244; RNA3: HF912245; RNA4: HF912246; RNA5: HG939489; RNA6: HG939490RNA1: NC_030660; RNA2: NC_030662; RNA3: NC_030661; RNA4: NC_030663; RNA5: NC_030658; RNA6: NC_030659Complete genomePPSMV-2Pistacia emaravirus Bpistacia virus BIsolate 55RNA1: MH727572; RNA2: MH727573; RNA3: MH727574; RNA4: MH727575; RNA5a: MH727576; RNA5b: MH727577; RNA6: MH727578; RNA7: MH727579Complete genomePiVBRaspberry leaf blotch emaravirusraspberry leaf blotch virusTaysideRNA1: FR823299; RNA2: FR823300; RNA3: FR823301; RNA4: FR823302; RNA5: FR823303; RNA6: KP970121; RNA7: KP970122; RNA8: KP970123RNA1: NC_029567; RNA2: NC_029558; RNA3: NC_029559; RNA4: NC_029560; RNA5: NC_029561; RNA6: NC_029571; RNA7: NC_029572; RNA8: NC_029573Complete genomeRLBVRedbud yellow ringspot-associated emaravirusredbud yellow ringspot-associated virusArkansasRNA1: JF795479; RNA2: JF795480; RNA3: JF795481; RNA4: JF795482; RNA5: KU904300RNA1: NC_038852; RNA2: NC_038856; RNA3: NC_038854; RNA4: NC_038853; RNA5: NC_038855Partial genomeRYRaVRose rosette emaravirusrose rosette virusArkansas+SEQISORNA1: HQ871942; RNA2: HQ871943; RNA3: HQ871944; RNA4: HQ871945; RNA5: KM007081; RNA6: KM007082; RNA7: KM007083RNA1: NC_015298; RNA2: NC_015299; RNA3: NC_015300; RNA4: NC_015301; RNA5: NC_034979; RNA6: NC_034980; RNA7; NC_034981Complete genomeRRV
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