Virome Characterization of a Collection of S. sclerotiorum from Australia

Abstract

Sclerotinia sclerotiorum is a devastating plant pathogen that attacks numerous economically important broad acre and vegetable crops worldwide. Mycoviruses are widespread viruses that infect fungi, including S. sclerotiorum. As there were no previous reports of the presence of mycoviruses in this pathogen in Australia, studies were undertaken using RNA_Seq analysis to determine the diversity of mycoviruses in 84 Australian S. sclerotiorum isolates collected from various hosts. After RNA sequences were subjected to BLASTp analysis using NCBI database, 285 contigs representing partial or complete genomes of 57 mycoviruses were obtained, and 34 of these (59.6%) were novel viruses. These 57 viruses were grouped into 10 distinct lineages, namely Endornaviridae (four novel mycoviruses), Genomoviridae (isolate of SsHADV-1), Hypoviridae (two novel mycoviruses), Mononegavirales (four novel mycovirusess), Narnaviridae (10 novel mycoviruses), Partitiviridae (two novel mycoviruses), Ourmiavirus (two novel mycovirus), Tombusviridae (two novel mycoviruses), Totiviridae (one novel mycovirus), Tymovirales (five novel mycoviruses), and two non-classified mycoviruses lineages (one Botrytis porri RNA virus 1, one distantly related to Aspergillus fumigatus tetramycovirus-1). Twenty-five mitoviruses were determined and mitoviruses were dominant in the isolates tested. This is not only the first study to show existence of mycoviruses in S. sclerotiorum in Australia, but highlights how they are widespread and that many novel mycoviruses occur there. Further characterization of these mycoviruses is warranted, both in terms of exploring these novel mycoviruses for innovative biocontrol of Sclerotinia diseases and in enhancing our overall knowledge on viral diversity, taxonomy, ecology, and evolution.

Metatranscriptomic reconstruction reveals RNA viruses with the potential to shape carbon cycling in soil

“…Viruses have been proposed, and used, as biocontrol agents for culling invasive organisms including fire ants, rabbits and moths (64)(65)(66). Viruses are also being investigated as biocontrol agents for devastating plant pathogens such as, Fusarium sp., Botrytis cinereal and Rosellinia necatrix (6,31,(67)(68)(69)(70)(71). Novel, environmentally derived viruses may be a source for new biotech tools and biocontrol agents.…”

Isolation, molecular characterization and virome analysis of culturable wood fungal endophytes in esca symptomatic and asymptomatic grapevine plants

“…We also identified a virus belonging to a group of viruses still unclassified hosting tetramycoviruses. They are characterized by a multipartite genome (4-5 segments were reported) each presenting a single ORF: RNA1 encodes for the RdRp, RNA2 encodes for a Per-Arnt-Sim-rich protein, RNA3 encodes a protein with a methyltransferase domain, RNA4 and five encode for proteins of unknown function (Kanhayuwa et al, 2015;Mu et al, 2018). In addition, from the discovery of the first member of this group, a number of new viruses belonging to this clade were reported, forming now a well-supported and independent group.…”

Evolutionary and ecological links between plant and fungal viruses

“…The mitoviruses are members of the family Narnaviridae, some of the simplest viruses known, comprising an RNA genome that expresses only one protein, an RNA-dependent RNA polymerase (RdRp). They are widespread and common in filamentous fungi; for example, a recent virome analysis of the plant pathogenic fungus Sclerotinia sclerotiorum found 25 different mitoviruses in this single fungal species (Mu et al, 2018).…”

“…Many families of the characterized fungal viruses have hosts that belong to the plant kingdom (Table 1). In addition to these families, recent metagenomic studies have added other families from the plant virus group: Benyviridae, Ophioviridae, Tymoviridae and Virgaviridae (Marzano et al, 2016;Mu et al, 2018). As the age of discovery continues, undoubtedly there will be more.…”

“…No reverse-transcribing viruses have been found in extant fungi, although endogenous retroelements are common and suggest a past history with these viruses (Ghabrial et al, 2015;Roossinck & Baz an, 2017). The most common viruses characterized from fungi are those with dsRNA genomes, but recent metagenomic studies are providing evidence of a broader range of virus types (Marzano et al, 2016;Mu et al, 2018).…”