Molecular characterization of a novel polymycovirus from the phytopathogenic fungus Setosphaeria turcica

Abstract A putative polymycovirus tentatively named Setosphaeria turcica polymycovirus 1 (StPmV1) was discovered from the phytopathogenic fungus Setosphaeria turcica. StPmV1 has a genome comprising 5 double stranded RNAs (dsRNAs). DsRNA1-3 each encodes a protein sharing significant but lower than 64% sequence identity with corresponding proteins from other polymycoviruses. DsRNA4-5 each encodes a protein with a sequence not conserved among polymycoviral proteins. However, the protein encoded by dsRNA4 is rich in proline (P), alanine (A), and serine (S) residues, which is a feature shared by the so-called PAS-rich proteins encoded by all polymycoviruses. Phylogeny reconstruction using the RNA-dependent RNA polymerases (RdRp) of accepted or putative polymycoviruses revealed that StPmV1 is most closely related to Plasmopara viticola lesion associated Polymycovirusmyco 1 (PvaPolymyco1), a putative polymycovirus recovered from the phytopathogenic oomycetes Plasmopara viticola. These data suggest that StPmV1 may represent a novel species of the genus Polymycovirus under the family Polymycoviridae. To our knowledge, this is the first polymycovirus reported from S. turcica.