Family: Botourmiaviridae
Genus: Penoulivirus
Distinguishing features
Penouliviruses have a mono-segmented genome, infect fungi, and are phylogenetically distinct from other botourmiaviruses. Apple ourmia-like virus 2 has been found in apple (Malus domestica) but it is not clear if the host of this virus is the plant or a fungus associated with the plant tissue (Wright et al., 2020).
Virion
No true virions are associated with penouliviruses since their genomes have no capsid protein gene.
Genome organization and replication
The Penicillium sumatrense ourmia-like virus 1 (PsOLV1) genome is a (+) RNA molecule of 2,976 nucleotides with 53% GC content. The complete genome sequence has a 5′ non-coding region (NCR) of 557 nt and a 3′-NCR of 94 nt. The virus genome contains a single ORF from nt positions 558 to 2 882, predicted to encode a polypeptide of 774 amino acids (88 kDa) that has similarity to the RNA-directed RNA polymerase (RdRP) of other penouliviruses (Nerva et al., 2019b). The Sclerotinia sclerotiorum ourmia-like virus 4 (SsOLV4) genome has been completely sequenced (2 892 nt) (Wang et al., 2020). The infectious clone of SsOLV4 could transfer among S. sclerotiorum strains via hyphal anastomosis, suggesting that only the RdRP-coding RNA segment is sufficient for transmission (Wang et al., 2020). Botrytis cinerea ourmia-like penoulivirus 1 (BcOLV1), Botrytis cinerea ourmia-like penoulivirus 2 and Botrytis cinerea ourmia-like penoulivirus 3, have genomes of 3 168 to 5 107 nt; BcOLV1 has an unusual long 5′-NCR of 2 242 nt (Ruiz-Padilla et al., 2021). Nine Plasmopara viticola lesion associated ourmia-like penouliviruses are included also in this genus with different genome sizes (Chiapello et al., 2020). Erysiphe necator associated ourmia-like virus 21 has a genome of 2 680 nt which contains open reading frames in both senses coding for a putative RNA-dependent RNA polymerase (RdRP) and three other putative proteins (Galán-Cubero et al., 2022). The Magnaporthe oryzae botourmiavirus 5 genome is 2 598 nts in length (Liu et al., 2020).
Biology
Penicillium sumatrense ourmia-like virus 1 infects the plant pathogenic fungus Penicillium sumatrense, and was isolated from samples of asymptomatic grapevine plants (Nerva et al., 2019b). Phaeoacremonium minimum ourmia-like virus 1, Epicoccum nigrum ourmia-like virus 2, and Neofusicoccum parvum ourmia-like virus 1 were isolated from samples of esca symptomatic grapevine plants, and Cladosporium uredinicola ourmia-like virus 2 from samples of asymptomatic grapevine plants (Nerva et al., 2019b). Sclerotinia sclerotiorum ourmia-like virus 4 was isolated from a sclerotium of a diseased oilseed rape infected by the plant pathogenic fungus Sclerotinia sclerotiorum (Wang et al., 2020). Phoma matteucciicola ourmia-like virus 1 infects the fungus Phoma matteucciicola (Zhou et al., 2020). Aspergillus neoniger ourmia-like virus 1 was discovered in an analysis of fungal public transcriptomes (Gilbert et al., 2019). Pyricularia oryzae ourmia-like virus 1 infects the fungus Pyricularia oryzae and was identified in host fungus isolated from wheat lesions (Ohkita et al., 2019). Magnaporthe oryzae ourmia-like virus 4 infects the plant pathogenic fungus Magnaporthe oryzae (Li et al., 2019). Phomopsis longicolla RNA virus 1 infects the fungus Phomopsis longicolla (Hrabáková et al., 2017). Apple ourmia-like virus 2 isolate WA1 was obtained from a survey in Malus domestica (apple) tissue showing symptoms of apple decline (Wright et al., 2020). Macrophomina phaseolina ourmia-like virus 3 infects the fungus Macrophomina phaseolina (Wang et al., 2021). Plasmopara viticola lesion associated ourmia-like penouliviruses were identified in grapevine leaves showing symptoms of downy mildew (oomycete Plasmopara viticola) infection (Chiapello et al., 2020). Erysiphe necator associated ourmia-like virus 21 was identified in grapevine leaves showing symptoms of powdery mildew (fungus Erysiphe necator) infection (Galán-Cubero et al., 2022). Magnaporthe oryzae botourmiavirus 5 was found in diseased rice leaf samples with the typical symptoms of rice blast (fungus Magnaporthe oryzae) (Liu et al., 2020).
Species demarcation criteria
Amino acid sequence identities of putative RdRP proteins between viruses belonging to different species in the genus Penoulivirus should be less than 90%.