Alphanudiviral segments found in transcriptomes of the two-spotted spider mite, Tetranychus urticae (Acari: Tetranychidae).

Nudiviruses (family Nudiviridae) are a diverse group of enveloped, rod-shaped viruses with double-stranded DNA genomes that infect a wide range of insects and crustaceans. These viruses are of significance both as biological control agents in agriculture and as agents of disease in aquaculture and insect rearing. In this work, we found four segments of a novel and divergent nudivirus identified through RNA-seq data from the two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae). The sequences of this virus were detected only in a subset of mite transcriptomes. The assembled segments covered a total of 100,780 bp, with 122 annotated ORFs, including all the 28 conserved nudiviral core genes. Phylogenetic analysis based on the predicted amino acid sequences of 17 selected nudiviral core genes placed the virus within the Alphanudivirus genus, in a clade containing nudiviruses identified from flea transcriptomes. This placement was confirmed by phylogenies of segment-specific concatenated core gene alignments. Indeed, the virus was designated as Tetranychus urticae alphanudivirus (TuNV). Transcriptional profiling revealed variable levels of transcriptional activity among genomic segments and viral genes. Arthropod gene homologs were found interspersed among nudiviral genes across all segments along with several unique genes. This genomic and phylogenetic characterization enhances our understanding of nudivirus diversity and evolution within arthropod hosts.