Molecular characterization of a novel citrivirus from citrus using next-generation sequencing

A novel positive-strand RNA virus infecting citrus with the tentative name "citrus leaf blotch virus 2" (CLBV-2), was identified in the present work. The complete genome sequence of CLBV-2 comprises 8,697 nucleotides (nt) excluding a poly(A) tail and three open reading frames (ORFs), showing the highest nucleotide sequence identity with the Actinidia strain (JN983456) of citrus leaf blotch virus (CLBV). The putative movement protein (ORF2), coat protein (ORF3), and 3' untranslated region (UTR) shared high sequence similarity with those of the extant CLBV isolates. In contrast, only low sequence similarity was observed in the 5' UTR and putative replicase polyprotein (ORF1) regions. The distant phylogenetic relationship between CLBV-2 and CLBV was deduced based on whole-genome nucleotide and whole-ORF1 amino acid sequence comparisons. Sequence comparisons suggest that CLBV-2 acquired an ORF2-ORF3-3' UTR region homologous to CLBV by recombination with of an unknown citrivirus. In view of the fact that this genomic recombination event appears to have occurred between members of different species in the genus Citrivirus, we propose that CLBV-2 should be considered a member of a distinct species.