Mycoviruses

Abstract

Viruses are tiny genetic elements that can have enormous impacts on living systems. Relative to viruses of prokaryotes and many other eukaryotes, mycoviruses have received less attention. Recent work, however, has shed light on how mycoviruses modify host phenotypes, the molecular basis for mycovirus–host interactions, and potential applications of mycoviruses for biocontrol in agriculture.

Known from most, but not all, phyla, mycoviruses are still underexplored in many fungal lineages. Mycovirus diversity is classified into 22 families of predominantly RNA viruses. Phenotypic effects vary and examples of mycovirus–host relationships span the parasitism–mutualism continuum, though mycovirus infection often appears asymptomatic in lab culture. However, either the literature is skewed toward or mycoviruses tend toward negative host effects, such as growth rate reduction or inducing hypovirulence. These phenotypic changes are typically associated with altered host gene expression induced by both virus and host. Hosts may respond to infection through the innate immune function of RNA silencing pathways. It is known that mycoviruses may also be able to manipulate third parties (i.e., plant or animal hosts) via their affiliation with fungi. Many mycoviruses have become endogenized into their host’s genome, and this process may be involved in facilitating horizontal gene transfer between fungi.