Members of the family Polymycoviridae are small viruses with multi-segmented and non-conventionally encapsidated double-stranded (ds) RNA genomes. Typically, polymycoviruses have four genomic segments, although some have up to eight. The genus Polymycovirus includes several species whose members infect fungi (ascomycetes and basidiomycetes), and oomycetes, altering host morphology, sporulation, growth and virulence. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the family Polymycoviridae, which is available at ictv.global/report/polymycoviridae

Coutts, RHA

Ictv Report Consortium

Kotta-Loizou, I

Journal of General Virology

English

Spiral - Imperial College Digital Repository

1ICTV Virus Taxonomy Profile: Polymycoviridae 2022Ioly Kotta- Loizou1,*, Robert H. A. Coutts2 and ICTV Report ConsortiumVIRIONMost polymycoviruses form non- conventional virions, whereby genomic dsRNA is coated by a viral protein (Table 1) [1–3]. Only Colletotrichum camelliae filamentous virus 1 is believed to have a filamentous capsid [4], 10–20 nm in width and >1000 nm in length (Fig. 1).GENOMEPolymycovirus genomes range from 7.5–12.5 kbp and comprise four to eight dsRNA segments. Each segment contains a single open reading frame (ORF) flanked by long non- coding regions (NCRs) with conserved termini (Fig. 2).The ORF of dsRNA 1 encodes an RNA- directed RNA poly-merase (RdRP) belonging to the protein family RdRP_1 (Pfam PF00680) and has three conserved motifs. The ORF of dsRNA 2 encodes a protein of unknown function containing a conserved N- terminus and a cysteine- rich, zinc finger- like motif. The ORF of dsRNA 3 encodes a methyl transferase, responsible for adding a capping structure to the 5′-termini of the positive- sense strands of viral dsRNAs [1, 2]. The ORF of dsRNA 4 encodes a proline–alanine–serine- rich protein (PASrp). When present, dsRNAs 5–8 encode proteins of unknown function that are non- homologous between different viruses.REPLICATIONPolymycoviruses were the first dsRNA viruses found to be infectious not only as purified entities but also as naked dsRNA [1, 3, 4]. Replication has not been characterized in detail. Virions accumulate in the cytoplasm.ICTV VIRUS TAXONOMY PROFILEKotta- Loizou et al., Journal of General Virology 2022;103:001747DOI 10.1099/jgv.0.001747Received 01 March 2022; Accepted 07 March 2022; Published 31 May 2022Author affiliations: 1Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, London SW7 2AZ, UK; 2Department of Clinical, Pharmaceutical and Biological Sciences, School of Life and Medical Sciences, University of Hertfordshire, Hatfield AL10 9AB, UK.*Correspondence: Ioly Kotta- Loizou,  i. kotta- loizou13@ imperial. ac. ukKeywords: Polymycoviridae; Polymycovirus; taxonomy; ICTV report.Abbreviations: (+), positive- sense; ds, double- stranded; NCR, non- coding region; ORF, open reading frame; PASrp, proline- alanine- serine- rich protein; RdRP, RNA- directed RNA polymerase.001747 © 2022This is an open- access article distributed under the terms of the Creative Commons Attribution License.ICTVAbstractMembers of the family Polymycoviridae are small viruses with multi- segmented and non- conventionally encapsidated double- stranded (ds) RNA genomes. Typically, polymycoviruses have four genomic segments, although some have up to eight. The genus Polymycovirus includes several species whose members infect fungi (ascomycetes and basidiomycetes), and oomycetes, altering host morphology, sporulation, growth and virulence. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the family Polymycoviridae, which is available at ictv.global/report/polymycoviridae.Table 1. Characteristics of members of the family PolymycoviridaeExample Aspergillus fumigatus tetramycovirus 1 (dsRNA 1: HG975302; dsRNA 2: HG975303; dsRNA 3: HG975304; dsRNA 4: HG975303), species Aspergillus fumigatus polymycovirus 1, genus PolymycovirusVirion Non- conventionally encapsidated dsRNA, coated with viral proteinGenome A total of 7.5–12.5 kbp of dsRNA in a multipartite genome (usually four segments, up to eight)Replication Both dsRNA and ssRNA can be isolated from infected fungal hosts. Virions accumulate in the cytoplasmTranslation From positive- sense transcripts of genomic dsRNAsHost range Fungi (ascomycetes and basidiomycetes), oomycetesTaxonomy Realm Riboviria; the genus Polymycovirus includes >9 speciesOPENACCESS2Kotta- Loizou et al., Journal of General Virology 2022;103:001747PATHOGENICITYPolymycovirus infection has been associated with various host alterations, including changes in pigmentation [1, 2, 4, 5], sectoring [1, 2], decreased host growth [4] and host virulence [4], as well as increased sporulation [5], host growth [2, 5] and host virulence [2]. Infection has also been reported to increase sensitivity to antifungals [3] and to the bacterium Pseudomonas aeruginosa [6]. Although the molecular mecha-nisms underpinning the above phenotypes have not been elucidated, there is evidence that polymycoviruses modulate host carbon, nitrogen and iron metabolism [5, 7]. Finally, polymycoviruses are targeted by the host RNA silencing machinery [8].TAXONOMYCurrent taxonomy: ictv.global/taxonomy. Viruses in the family Polymycoviridae are most closely related to Hadaka virus 1 isolates, positive- sense (+) single- stranded (ss) RNA viruses in the family Hadakaviridae. Polymycovirus- encoded RdRPs are also related to those of (+)ssRNA viruses in the families Astroviridae, Caliciviridae and Picornaviridae, and of dsRNA viruses in the family Partitiviridae in the phylum Pisuviricota. The GDNQ motif, typically found in the RdRP of negative- sense ssRNA viruses of the order Mononegavirales, is conserved in all members of the family Polymycoviridae, instead of the GDD motif found in most dsRNA and (+)ssRNA viruses. Polymycoviruses appear to be intermediate between dsRNA and (+)ssRNA viruses, as well as between encapsidated and capsidless RNA viruses [1].RESOURCESFull ICTV Report on the family Polymycoviridae: ictv.global/ report/polymycoviridae.Funding informationProduction of this summary, the online chapter and associated resources was funded by a grant from the Wellcome Trust (WT108418AIA).AcknowledgementsMembers of the ICTV Report Consortium are Stuart G. Siddell, Elliot J. Lefkowitz, Peter Simmonds, F. Murilo Zerbini, Donald B. Smith and Sead Sabanadzovic.Conflicts of interestThe authors declare that there are no conflicts of interest.Fig. 1. Polymycovirus virions. (a) Atomic force microscopy of purified Aspergillus fumigatus tetramycovirus 1 non- conventional virions; white arrows indicate the viral protein coating the dsRNA genome. (Adapted from Ref. [1]). (b) Transmission electron microscopy of purified Colletotrichum camelliae filamentous virus 1 conventional virions. (Adapted from Ref. [4] under CC BY 4.0).Fig. 2. Genome organization of Aspergillus fumigatus tetramycovirus 1. ORFs are represented by rectangular boxes with internal light- coloured boxes representing known and/or predicted motifs and domains, such as the RdRP_1 motif (PF00680) in dsRNA 1 and Methyltransf_25 (PF13649) in dsRNA 3. Vertical lines indicate conserved RdRP motifs.References 1. Kanhayuwa L, Kotta- Loizou I, Özkan S, Gunning AP, Coutts RHA. A novel mycovirus from Aspergillus fumigatus contains four unique dsRNAs as its genome and is infectious as dsRNA. Proc Natl Acad Sci U S A 2015;112:9100–9105.  2. Kotta- Loizou I, Coutts RHA. Studies on the virome of the entomopatho-genic fungus Beauveria bassiana reveal novel dsRNA elements and mild hypervirulence. PLoS Pathog 2017;13:e1006183.  3. Niu Y, Yuan Y, Mao J, Yang Z, Cao Q, et al. Characterization of two novel mycoviruses from Penicillium digitatum and the related fungicide resist-ance analysis. Sci Rep 2018;8:5513.  4. Jia H, Dong K, Zhou L, Wang G, Hong N, et al. A dsRNA virus with filamen-tous viral particles. Nat Commun 2017;8:168.  5. Filippou C, Diss RM, Daudu JO, Coutts RHA, Kotta- Loizou I. The polymycovirus- mediated growth enhancement of the entomopatho-genic fungus Beauveria bassiana is dependent on carbon and nitrogen metabolism. Front Microbiol 2021;12:606366.  6. Nazik H, Kotta- Loizou I, Sass G, Coutts RHA, Stevens DA. Virus infec-tion of Aspergillus fumigatus compromises the fungus in intermicrobial competition. Viruses 2021;13:686.  7. Patil RH, Kotta- Loizou I, Palyzová A, Pluháček T, Coutts RHA, et  al. Freeing Aspergillus fumigatus of polymycovirus infection renders it more resistant to competition with Pseudomonas aeruginosa due to altered iron- acquiring tactics. J Fungi (Basel) 2021;7:497.  8. Özkan S, Mohorianu I, Xu P, Dalmay T, Coutts RHA. Profile and func-tional analysis of small RNAs derived from Aspergillus fumigatus infected with double- stranded RNA mycoviruses. BMC Genomics 2017;18:416. 

ICTV virus taxonomy profile: polymycoviridae 2022.

http://spiral.imperial.ac.uk/bitstream/10044/1/97523/2/jgv001747.pdf

ICTV virus taxonomy profile: polymycoviridae 2022.

Abstract

Similar works

Full text

Available Versions

Spiral - Imperial College Digital Repository