ICTV Report on the (+) RNA virus family Yadokariviridae

Yadokariviridae is a family of capsidless non-segmented positive-sense (+) RNA viruses in the order Yadokarivirales (Table 1.Yadokariviridae). The family includes the genera Alphayadokarivirus and Betayadokarivirus. Yadokarivirids lack their own capsid protein but hijack the capsids from phylogenetically distant double-stranded RNA (dsRNA) viruses on which yadokarivirids rely for their viability. Heterocapsids, which include the yadokarivirid RNA-directed RNA polymerase (RdRP) and replicative form dsRNA, are the likely replication site of yadokarivirids. Nevertheless, yadokarivirids show phylogenetic affinity to positive-sense (+) RNA viruses in the phylum Pisuviricota. Thus, yadokarivirids are evolutionary unique viruses that may have switched their replication site from host membranous structures to the heterocapsid, as with a dsRNA virus. While the known capsid donor dsRNA viruses span at least five diverse families, each yadokarivirid relies on a distinct species of dsRNA virus. Yadokarivirids play a complex role in the tripartite interaction with their capsid donor viruses and host fungi.