Molecular Characterization of a Novel Partitivirus and a Fusarivirus Co-infected in the Nigrospora Sphaerica Fungus

Abstract Here we reported the molecular characterization of two novel mycoviruses co-infected in a plant pathogenic fungus, Nigrospora sphaerica that were designated as Nigrospora sphaerica fusarivirus 1 (NsFV1) and Nigrospora sphaerica partitivirus 1 (NsPV1), respectively. NsFV1 has an undivided genome of 6,147 bp, excluding the polyA tail, and was predicted to contain two nonoverlapping open reading frames (ORF1 and 2). The larger ORF1 encoded a polyprotein containing a conserved RNA-dependent RNA polymerase (RdRp) and a helicase domain that have functions for RNA replication, and the smaller ORF2 encoded a putative protein with an unknown function. The NsPV1 was consists of two genome segments, which were in lengths of 1,796 bp and 1,455 bp, respectively. Each of the two dsRNAs had a single ORF and were deduced to encode proteins with homology to viral RdRp and coat protein (CP), respectively, in the family Partitiviridae. Phylogenetic analysis showed that NsFV1 was placed within the newly proposed family Fusariviridae, while NsPV1 was belonging to the genus Gammapartitivirus in the family Partitiviridae. This was the first description of mycovirses infected the fungus N. sphaerica.