Family: Botourmiaviridae
Genus: Magoulivirus
Distinguishing features
Magouliviruses have a mono-segmented genome and infect fungi. Some members of the genus have been identified in association with grapevine leaves affected by the oomycete Plasmopara viticola. Magouliviruses are phylogenetically distinct from other botourmiaviruses. Apple ourmia-like virus 3 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). The monopartite genome of Magnaporthe oryzae ourmia-like virus 1 has a poly-A tail at the 3′-end (Illana et al., 2017).
Virion
No true virions are associated with magouliviruses since their genomes have no capsid protein gene.
Genome organization and replication
Magnaporthe oryzae ourmia-like virus 1 (MOLV1) genome is a positive-sense polyadenylated RNA molecule of 2 364 nt, excluding the poly (A) tail. The 5′ and 3′ non-coding regions of MOLV1 are 116 nt and 430 nt long, respectively. The MOLV1 genome has a single open reading frame (ORF) from nt positions 117 to 1 931, predicted to encode a polypeptide of 605 aa (67.12 kDa). This MOLV1 protein contains the conserved domains of the RNA-directed RNA polymerase (RdRP) present in (+) RNA viruses, including the highly conserved core domain GDD in motif VI (Illana et al., 2017). Magnaporthe oryzae botourmiavirus 2 genome is 2 250 nt in length (Liu et al., 2020). The genomes of Botrytis cinerea ourmia-like virus 6, Botrytis cinerea ourmia-like virus 7 and Botrytis cinerea ourmia-like virus 8 are 2 100 to 2 706 nt with a RdRP of 515 to 692 aa (Ruiz-Padilla et al., 2021). Twenty-five Plamospara viticola lesion associated magouliviruses are also included in this genus, which have different genome sizes although all encode only a single RdRP (Chiapello et al., 2020). Apple ourmia-like virus 3 genome is 3 067 nt in length with a very long 3′-non-coding region of 1 016 nt and encoding an RdRP of 674 aa (Wright et al., 2020). The full-length sequence of Fusarium oxysporum ourmia-like virus 1 is 2 712 nt with only one large ORF encoding a RdRP of 701 amino acids (Zhao et al., 2020). Armillaria mellea ourmia-like virus 2 (AmOlV2) has a genome of 3 162 nt and a RdRP of 731 amino acids (Linnakoski et al., 2021). Heterobasidion ourmia-like virus 1 genome is 2 532 nt with a single ORF encoding a 641 aa long putative RdRP (Sutela et al., 2021). The complete genome of Botryosphaeria dothidea ourmia-like virus 1 is 2 797 nt in length and contains a single ORF of 1 929 nt, putatively encoding a RdRP of 642 amino acids (Lian et al., 2021).
Biology
Magnaporthe oryzae ourmia-like viruses infect Magnaporthe oryzae (Illana et al., 2017, Liu et al., 2020). Rhizoctonia solani ourmia-like virus 1 was identified in a metatranscriptomic analysis of the fungus Rhizoctonia solani (Marzano et al., 2016). Acremonium sclerotigenum ourmia-like virus 1, Cladosporium cladosporioides ourmia-like virus 2, and Phaeoacremonium minimum ourmia-like virus 2 were identified in samples of esca symptomatic grapevine plants, and Cladosporium cladosporioides ourmia-like virus 1 in samples of esca asymptomatic grapevine plants (Nerva et al., 2019b). Penicillium citrinum ourmia-like virus 1 infects the fungus Penicillium citrinum (Nerva et al., 2019a). Colletotrichum gloeosporioides ourmia-like virus 1 infects the plant pathogenic fungus Colletotrichum gloeosporioides (Guo et al., 2019). Botrytis cinerea ourmia-like virus 6, Botrytis cinerea ourmia-like virus 7 and Botrytis cinerea ourmia-like virus 8 were identified in B. cinerea strains isolated from grapevine (Ruiz-Padilla et al., 2021). Macrophomina phaseolina ourmia-like virus 2 infects the fungus Macrophomina phaseolina (Wang et al., 2021). Plamospara viticola lesion associated magouliviruses were identified in grapevine leaves showing symptoms of downy mildew (oomycete Plasmopara viticola) infection (Chiapello et al., 2020). Apple ourmia-like virus 3 was obtained from a survey in Malus domestica (apple) tissue showing symptoms of apple decline (Wright et al., 2020). Fusarium oxysporum ourmia-like virus 1 was isolated from bitter gourd, showing symptoms of Fusarium wilt disease (Zhao et al., 2020). Armillaria mellea ourmia-like virus 2 infects the basidiomycete fungus Armillaria mellea (Linnakoski et al., 2021). Heterobasidion ourmia-like virus 1 infects the basidiomycete fungus Heterobasidion parviporum (Sutela et al., 2021). Botryosphaeria dothidea ourmia-like virus 1was found in an apple-infecting ascomycete fungus (Botryosphaeria dothidea) showing no apparent disease symptoms (Lian et al., 2021).
Species demarcation criteria
Amino acid sequence identities of putative RdRP proteins between viruses belonging to different species of the genus Magoulivirus are less than 90%.