Co-infection of a hypovirulent isolate of Sclerotinia sclerotiorum with a new botybirnavirus and a strain of a mitovirus. Issue 1 (December 2016)

• Record Type: Journal Article
• Authors: Ran, Hongchang; Liu, Lijiang; Li, Bo; Cheng, Jiasen; Fu, Yanping; Jiang, Daohong; Xie, Jiatao
• Is Part Of: Virology journal. Volume 13:Issue 1(2016)
• Page Start: 1
• Page End: 10
• Publication Date: 2016-12
• Subjects: Mycovirus -- Botybirnavirus -- Mitovirus -- Mixed-infection -- Hypovirulence -- Sclerotinia sclerotiorum; Virology -- Periodicals; 579.2
• DOI: 10.1186/s12985-016-0550-2
• Languages: English
• ISSNs: 1743-422X

Abstract

Abstract Background Sclerotinia sclerotiorum, a notorious plant fungal pathogen, causes yield loss of many crops and vegetables, and is a natural host of a diverse viruses with positive-sense RNA (+ssRNA), negative-sense RNA (−ssRNA), double-stranded RNA (dsRNA), or DNA genomes. Mixed-infection with multiple related or unrelated mycoviruses is a common phenomenon inS. sclerotiorum . However, a single strain co-infected with dsRNA and + ssRNA viruses has not been reported inS. sclerotiorum . Results We report two unrelated viruses, Sclerotinia sclerotiorum botybirnavirus 2 (SsBRV2) with a bipartite dsRNA genome and Sclerotinia sclerotiorum mitovirus 4 (SsMV4/AH16) with a + ssRNA genome, which were originally detected in a single hypovirulent strain AH16 ofS. sclerotiorum . SsMV4/AH16 has a typical genome of mitovirus and is a strain of mitovirus SsMV4. The genome of SsBRV2 consists of two separated dsRNA segments. The large dsRNA segment is 6159 bp in length and only has a single open reading frame (ORF) encoding a putative 1868-aa polyprotein with a conserved RNA dependent RNA polymerase (RdRp) domain. The small dsRNA segment is 5872 bp in length and encodes a putative 1778-aa protein. Phylogenetic analysis using RdRp conserved domain sequences revealed that SsBRV2 is phylogenetically related to the previously reported three bipartite viruses SsBRV1, Botrytis porri RNA virus 1 (BpRV1), and soybean leaf-associated botybirnavirus 1 (SlaBRV1). Electron microscopy demonstrated that SsBRV2 forms rigid spherical virions with a diameter of approximately 40 nm in infected mycelia. The virion of SsBRV2 was successfully introduced into a virus-free strain, which provides conclusive evidence that SsBRV2 confers hypovirulence on phytopathogenic fungusS. sclerotiorum . Conclusions A bisegmented dsRNA virus (SsBRV2/AH16) and a nonsegmented + ssRNA virus (SsMV4/AH16) were characterized in a hypovirulent strain AH16 ofS. sclerotiorum . SsMV4/AH16 is a strain of a reported mitovirus, whereas SsBRV2 is a new botybirnavirus. SsBRV2 is the causal agent of hypovirulence onS. sclerotiorum . Our findings supplied a first evidence that a singleS. sclerotiorum strain is co-infected by dsRNA and + ssRNA mycoviruses.