Characterization of a multi-segmented rod-shaped mycovirus within the order Martellivirales largely accommodating plant viruses

The order Martellivirales in the Riboviria realm includes seven established families. The viruses in this order have a single-stranded positive-sense RNA genome and infect animals, plants, or fungi. In this study, we characterized Aspergillus flavus vivivirus 1 (AfViV1), an RNA virus infecting Aspergillus flavus that presumably belongs to the proposed “Viviviridae” family in the Martellivirales order. In previous reports, multiple RNA-dependent RNA polymerase (RdRP) sequences related to “Viviviridae” were mainly identified from metatranscriptome data. However, their virological characteristics were not disclosed. Our analysis showed that the AfViV1 virion exhibited a rod-shaped structure with varying lengths and identified the coat protein (CP) encoded by RNA12 of AfViV1. Using the AfViV1-CP sequence, we detected several potential CP sequences from viruses in the suggested “Viviviridae“ family based on sequence read archive (SRA) data. These data suggest that viruses in this family have similar rod-shaped structures. Interestingly, the AfViV1-CP amino acid sequence was not significantly similar to the known viral CP. However, the predicted structure was similar to rod-shaped viruses in the Potyviridae (Patatavirales) and Closteroviridae (Martellivirales) families (and orders). Our analysis describes the first multi-segmented fungal ssRNA virus with rod-shaped particles and expands the morphological diversity of fungal RNA viruses. Additionally, this study highlights the similarities between fungal and plant viruses, suggesting their deep relationships concerning host range, host adaptation, and more.