Molecular characterization of a novel totivirus infecting the basal fungus Conidiobolus heterosporus

Mycoviruses are widely distributed in fungi, but only a few mycoviruses have been reported in basal fungi to date. Here, we characterized a novel totivirus isolated from the basal fungus Conidiobolus heterosporus, and we designated this virus as "Conidiobolus heterosporus totivirus 1" (ChTV1). The complete genome of ChTV1 contains two discontinuous open reading frames (ORFs), ORF1 and ORF2, encoding a putative coat protein (CP) and a putative RNA-dependent RNA polymerase (RdRP), respectively. Phylogenetic analysis based on RdRP sequences showed that ChTV1 clustered with members of the genus Totivirus. The RdRP of ChTV1 has 51% sequence identity to that of Trichoderma koningiopsis totivirus 1 (TkTV1), which is the highest among mycoviruses. However, TkTV1 formed a distinct cluster with Wuhan insect virus 27, with 63% RdRP sequence identity, although Wuhan insect virus 27 has not been described, and its host represents a different kingdom. Therefore, we propose that ChTV1 is a new member of the genus Totivirus, family Totiviridae.