Mitoviruses (Mitoviridae)

Members of the genus Mitovirus contain the simplest genomes of any autonomous, protein-encoding RNA virus: they encode only RNA-dependent RNA polymerase for their own replication, which takes place in mitochondria of many fungi and some plants. Their single-stranded RNA genomes are small, usually less than 3 kb, and are not encapsidated in protein capsids. Many are symptomless in their hosts, but some cause discernable disease in fungi. They appear to be ancient in origin, most closely related the yeast-infecting narnaviruses and the plant-infecting ourmiaviruses, and an offshoot of the bacterial leviviruses.