Complete nucleotide sequence and experimental host range of Okra mosaic virus

Okra mosaic virus (OkMV) is a tymovirus infecting members of the family Malvaceae. Early infections in okra (Abelmoschus esculentus) lead to yield losses of 12-19.5%. Besides intensive biological characterizations of OkMV only minor molecular data were available. Therefore, we determined the complete nucleotide sequence of a Nigerian isolate of OkMV. The complete genomic RNA (gRNA) comprises 6,223 nt and its genome organization showed three major ORFs coding for a putative movement protein (MP) of M r 73.1 kDa, a large replication-associated protein (RP) of M r 202.4 kDa and a coat protein (CP) of M r 19.6 kDa. Prediction of secondary RNA structures showed three hairpin structures with internal loops in the 5'-untranslated region (UTR) and a 3'-terminal tRNA-like structure (TLS) which comprises the anticodon for valine, typical for a member of the genus Tymovirus. Phylogenetic comparisons based on the RP, MP and CP amino acid sequences showed the close relationship of OkMV not only to other completely sequenced tymoviruses like Kennedya yellow mosaic virus (KYMV), Turnip yellow mosaic virus (TYMV) and Erysimum latent virus (ErLV), but also to Calopogonium yellow vein virus (CalYVV), Clitoria yellow vein virus (CYVV) and Desmodium yellow mottle virus (DYMoV). This is the first report of a complete OkMV genome sequence from one of the various OkMV isolates originating from West Africa described so far. Additionally, the experimental host range of OkMV including several Nicotiana species was determined.