Molecular Characterization of a Novel Polymycovirus From Penicillium janthinellum With a Focus on Its Genome-Associated PASrp

Abstract

The genus Polymycovirus of the family Polymycoviridae accommodates fungal RNA viruses with different genomic segment numbers (four, five, or eight). It is suggested that four members form no true capsids and one forms filamentous virus particles enclosing double-stranded RNA (dsRNA). In both cases, viral dsRNA is associated with a viral protein termed "proline-alanine-serine-rich protein" (PASrp). These forms are assumed to be the infectious entity. However, the detailed molecular characteristics of PASrps remain unclear. Here, we identified a novel five-segmented polymycovirus, Penicillium janthinellum polymycovirus 1 (PjPmV1), and characterized its purified fraction form in detail. The PjPmV1 had five dsRNA segments associated with PASrp. Density gradient ultracentrifugation of the PASrp-associated PjPmV1 dsRNA revealed its uneven structure and a broad fractionation profile distinct from that of typical encapsidated viruses. Moreover, PjPmV1-PASrp interacted in vitro with various nucleic acids in a sequence-non-specific manner. These PjPmV1 features are discussed in view of the diversification of genomic segment numbers of the genus Polymycovirus.

Phenotypic and Molecular Biological Analysis of Polymycovirus AfuPmV-1M From Aspergillus fumigatus: Reduced Fungal Virulence in a Mouse Infection Model

“…The majority of characterized mycoviruses of plant-pathogenic fungi have double-stranded RNA (dsRNA) genomes. Mycoviruses with dsRNA genomes have been classified into eight families (the families Totiviridae, Partitiviridae, Chrysoviridae, Amalgaviridae, Curvulaviridae, Reoviridae, Megavirnaviridae, and Polymycoviridae; Several unsigned viruses including AfuPmV-1 have recently been established as a new family Polymycoviridae (Zhai et al, 2016;Jia et al, 2017;Kotta-Loizou and Coutts, 2017b;Niu et al, 2018;Zoll et al, 2018;Mahillon et al, 2019;Sato et al, 2020) (International Committee on Taxonomy of Viruses (ICTV) 1 . Although many mycoviruses do not appear to cause symptoms in their hosts, some affect mycelial growth, sporulation, and pigmentation, while in some botanical pathogenic fungi, mycoviruses have been shown to reduce their virulence in plant hosts (Pearson et al, 2009).…”

Molecular characterization of a novel polymycovirus from the phytopathogenic fungus Setosphaeria turcica

“…Polymycoviriruses constitute a family of double-stranded RNA (dsRNA) viruses that infect a wide range of fungi (https://talk.ictvonline.org/taxonomy). Unlike most other dsRNA viruses, polymycoviriruses do not form isometric virions [1][2][3][4][5][6][7][8][9]. Instead, they encode a protein overrepresented by proline (P), alanine (A), and serine (S) residues.…”

“…In the case of Colletotrichum camelliae lamentous virus 1 (CcFV1), this PAS-rich protein (PASrp) encapsulates polymycoviriral dsRNAs into lamentous particles [3]. In most other cases, PASrp coats but not encapsulates viral dsRNAs [1][2][4][5][6][7][8][9]. Moreover, polymycoviriruses have a RNAdependent RNA polymerase (RdRp) more closely related to the RdRp of positive-sense single stranded RNA (+ ssRNA) viruses than to those encoded by other dsRNA viruses.…”

“…At least some polymycoviriruses are infectious as naked genomic dsRNAs [1,3]. These features have led to the idea that polymycoviriruses may represent an evolutionary intermediate between dsRNA and + ssRNA viruses and between capsidated and capsid-less viruses [1,3,8]. Polymycoviruses show a great exibility in genome arrangement.…”

“…For example, Aspergillus fumigatus tetramycovirus-1 (AfuTmV-1), the type species of the family Polymycoviridae, has a genome consisting of 4 dsRNAs [1]. The genome of many other polymycoviriruses, however, have 1-3 additional dsRNAs, which encode proteins not conserved among polymycoviriruses [2][3][4][5][6][7][8][9]. Although the effects of most polymycoviriruses on the growth and pathogenicity of their host fungi remain poorly characterized, some polymycoviriruses have been found to confer hypo-or hypervirulence to their hosts [1][2][3][4].…”