Letter to the editor: Bean-associated cytorhabdovirus and papaya cytorhabdovirus are strains of the same virus

BEJERMAN, NICOLÁS; DIETZGEN, RALF G.

Viruses

MDPI AG

Año: 2019 vol. 11

Recently, Alves-Freitas and colleagues [1] reported the complete genome sequence of a newcytorhabdovirus associated with a common bean in Brazil (GenBank accession number MK202584)which they tentatively named bean-associated cytorhabdovirus (BaCV). These authors reportedthat there was a low level of sequence identity with other cytorhabdoviruses (15-39%) and thatRNA-dependent RNA polymerase (RdRp) phylogeny showed that the BaCV clustered most closelywith yerba mate chlorosis-associated virus (YmCaV) and rice stripe mosaic virus (RSMV). Based onthese results, the authors suggested that BaCV should be taxonomically classified as a new species inthe genus Cytorhabdovirus. However, when we subjected BaCV protein sequences to Blastp analysis,the top hit (organism) was papaya cytorhabdovirus (PCRV) (GenBank accession number MH282832),whose complete genome sequence has been available in GenBank since October 1, 2018, almost threemonths before the manuscript describing BaCV was submitted to Viruses; the authors of the BaCV studymay have overlooked the GenBank submission, since the work describing papaya cytorhabdovirus hasnot yet been published. This finding prompted us to further investigate the relationship between BaCVand PCRV. The genomic organization of both viruses, as well as the gene junction sequences are verysimilar. Moreover, when analogous genes of both viruses were compared to each other, the sequenceidentity was always above 92%, and as high as 96%, for the nucleocapsid protein (N) gene, and 97%for glycoprotein (G) and RdRp genes/proteins (Table 1), which suggests that BaCV and PCRV arestrains of the same virus. Viruses assigned to different species within the genus Cytorhabdovirushave a minimum nucleotide sequence divergence of >50% in cognate genes [2], which is clearlynot the case here. Interestingly, both viruses have a high amino acid sequence identity (over 89%)with virus-like sequences associated with the whitefly Bemisia tabaci available in GenBank (KJ994257;KJ994260; KJ994261; KJ994263; KJ994264 accession numbers). Phylogenetic analysis showed that the N(Figure 1A) and RdRp (Figure 1B) amino acid sequences of BaCV, PCRV, and Bemisia tabaci virus-likesequences (BTCRV) cluster together in a separate clade, indicating that these viruses are closely related.This phenomenon indicates that BaCV and PCRV are strains of the same virus and that Bemisia tabaci isa likely potential vector of these viruses (Figure 1B).