A geminivirus-related DNA mycovirus that confers hypovirulence to a plant pathogenic fungus

TLDR

Mycoviruses can induce hypovirulence in fungal pathogens, yet until now only RNA viruses had been reported, with no DNA mycoviruses known. This study reports a circular single‑stranded DNA mycovirus associated with hypovirulence in the plant‑pathogenic fungus *Sclerotinia sclerotiorum*. The 2166‑nt genome encodes a replication initiation protein and coat protein, and polyethylene glycol‑mediated transfection of fungal protoplasts with purified virions or viral DNA successfully introduced the virus. Phylogenetic analysis places the virus in the geminivirus clade yet it differs in genome organization and particle morphology, demonstrating a novel DNA mycovirus that expands the toolbox for fungal manipulation and plant disease control while broadening our understanding of virus ecology.

Abstract

Mycoviruses are viruses that infect fungi and have the potential to control fungal diseases of crops when associated with hypovirulence. Typically, mycoviruses have double-stranded (ds) or single-stranded (ss) RNA genomes. No mycoviruses with DNA genomes have previously been reported. Here, we describe a hypovirulence-associated circular ssDNA mycovirus from the plant pathogenic fungus Sclerotinia sclerotiorum . The genome of this ssDNA virus, named Sclerotinia sclerotiorum hypovirulence-associated DNA virus 1 (SsHADV-1), is 2166 nt, coding for a replication initiation protein (Rep) and a coat protein (CP). Although phylogenetic analysis of Rep showed that SsHADV-1 is related to geminiviruses, it is notably distinct from geminiviruses both in genome organization and particle morphology. Polyethylene glycol-mediated transfection of fungal protoplasts was successful with either purified SsHADV-1 particles or viral DNA isolated directly from infected mycelium. The discovery of an ssDNA mycovirus enhances the potential of exploring fungal viruses as valuable tools for molecular manipulation of fungi and for plant disease control and expands our knowledge of global virus ecology and evolution.