Exploring the Genomics of Marnaviridae Family: Identification, Characterization, and Taxonomic Implications.

In this study, we characterized sequences similar to Marnaviridae obtained from water samples in the state of São Paulo, Brazil. Sixteen complete or nearly complete genomes were determined, all of them positive-sense single-stranded RNA, with lengths between 7074 and 10,198 base pairs, containing one or two open reading frames (ORFs). The amino acid sequences derived from the ORFs showed similarity and protein domains typical of the Marnaviridae family. Phylogenetic analysis based on RNA-dependent RNA polymerase (RdRp) revealed clusters closely related to viruses that have not yet been classified by the International Committee on Taxonomy of Viruses (ICTV). Some sequences showed proximity to established genera such as Salicharnavirus, Locarnavirus, and Labynarvirus, while others formed three distinct clades, suggesting the presence of new genera. Furthermore, one sequence displayed an RdRp identity of less than 90% and a capsid identity of less than 75%, indicating that it represents a novel species related to Marnaviridae. These findings expand current knowledge of Marnaviridae diversity, contributing to a better understanding of evolutionary relationships and emphasizing the need for taxonomic reorganization.