Mycoviromic Analysis Unveils Complex Virus Composition in a Hypovirulent Strain of Sclerotinia sclerotiorum

Abstract

Mycoviruses are ubiquitous in pathogenic fungi including Sclerotinia sclerotiorum. Using RNA sequencing, more mycoviruses have been identified in individual strains, which were previously reported to be infected by a single mycovirus. A hypovirulent strain of S. sclerotiorum, HC025, was previously thought to harbor a single mitovirus, Sclerotinia sclerotiorum mitovirus 1 (SsMV1), based on the analysis of the conventional dsRNA extraction method. We found HC025 to be co-infected by five mycoviruses. In addition to SsMV1, four mycoviruses were identified: Sclerotinia sclerotiorum narnavirus 4 (SsNV4), Sclerotinia sclerotiorum negative-stranded RNA virus 1 (SsNSRV1), Sclerotinia sclerotiorum ourmia-like virus 14 (SsOLV14), and SsOLV22. Three mycoviruses including SsNV4, SsNSRV1, and SsOLV14 share high replicase identities (more than 95%) with the previously reported corresponding mycoviruses, and SsOLV22 shows lower identity to the known viruses. The complete genome of SsOLV22 is 3987 nt long and contains a single ORF-encoded RdRp, which shares 24.84% identity with the RNA-dependent RNA polymerase (RdRp) of Hubei narna-like virus 10 (query coverage: 26%; e-value: 8 × 10−19). The phylogenetic tree of RdRp suggests that SsOLV22 is a new member within the family Botourmiaviridae. All of the mycoviruses except for SsNSRV1 could horizontally co-transfer from HC025 to the virulent strain Ep-1PNA367 with hypovirulent phenotypes, and converted a later strain into a hypovirulent strain. In summary, we molecularly characterized the hypovirulent strain HC025 and identified five RNA mycoviruses including a new member within Botourmiaviridae.

Molecular characterization of a novel fungal alphaflexivirus reveals potential inter-species horizontal gene transfer

“…Strain 32–9 was finally confirmed to be coinfected with two mycoviruses, SsAFV2 and SsOLV22 (Sclerotinia sclerotiorum ourmia-like virus 22, OK165499). The obtained genome of SsOLV22 is 3, 516 nt long and has a 96.7% nucleotide identity to the previously reported SsOLV22 infecting strain HC025 of S. sclerotiorum ( Wang et al., 2022 ). We recorded the two newly detected viral sequences in the GenBank database with the accession numbers OQ865609 for SsAFV2 and OQ869265 for SsOLV22.…”

Characterization of a Fungal Virus Representing a Novel Genus in the Family Alphaflexiviridae

“…The following supporting information can be downloaded at: . Table S1: Details of viruses referred to in this study [ 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 ].…”