Molecular characterization of a novel umbra-like virus from Thuja orientalis (arborvitae) in South Korea

A novel umbra-like virus was identified in arborvitae in South Korea using RNA sequencing (RNA-seq). The virus identified was tentatively named "arborvitae umbra-like virus" (AULV) and contained a 4,300-nucleotide genome organized into four non-structural open reading frames (ORFs). Cloning and Sanger sequencing were used to confirm the viral contig sequence and determine the size of the genome. Genome analysis indicated that ORF2 encodes an RNA-dependent RNA polymerase that is probably expressed through ribosomal frameshifting. ORF3 encodes a putative long-distance movement protein, while the functions of ORFs 1 and 4 are unknown. The virus lacks a coat protein gene. The genome of AULV shares 27.3%-48.4% nucleotide sequence identity with closely related umbraviruses. Phylogenetic analysis based on the complete genome sequences and amino acid sequences of the RNA-dependent RNA polymerase revealed that AULV forms a monophyletic lineage with Guiyang paspalum paspaloides tombus-like virus (GPpTV1). We suggest that AULV is a novel umbra-like virus belonging to the family Tombusviridae.