Taro vein chlorosis virus: characterization and variability of a new nucleorhabdovirus

Sequencing of the monopartite RNA genome of a Fijian isolate of Taro vein chlorosis virus (TaVCV) confirmed that it is a definitive rhabdovirus with most similarity to members of the genus Nucleorhabdovirus. The TaVCV 12 020 nt negative-sense RNA genome contained six ORFs in the antigenomic sequence, equivalent to the N, P, 3, M, G and L genes that have been identified in other rhabdoviruses. The putative gene products had highest similarity to those of the nucleorhabdovirus Maize mosaic virus. A characteristic 3'-AAUUCUUUUUGGGUUGU/A-5' sequence was identified in each of the intergenic regions and the TaVCV leader and trailer sequences comprised 140 and 61 nt, respectively. Assignment of TaVCV to the genus Nucleorhabdovirus was supported by thin-section electron microscopy of TaVCV-infected taro leaves, which identified virions budding from nuclear membranes into the perinuclear space. Variability studies identified high levels of TaVCV sequence diversity. Within the L gene of 20 TaVCV isolates from Fiji, the Federated States of Micronesia, New Caledonia, Papua New Guinea, Solomon Islands and Vanuatu, maximum variability at the nucleotide level was 27.4 %. Within the N gene, maximum variability among 15 isolates at the nucleotide level was 19.3 %. The high level of TaVCV variability observed suggested that the introduction of TaVCV to the Pacific Islands was not a recent occurrence.