Mutation of the allexivirus-specific P40 gene of Wineberry latent virus, an isolate of Blackberry virus E, greatly reduces virus multiplication

Abstract

The complete sequence of Wineberry latent virus (WLV), a previously reported but uncharacterised Rubus-infecting virus with flexuous particles, has been determined. Analysis shows WLV to have 76% overall nucleotide sequence identity to the more recently discovered Blackberry virus E, an allexivirus belonging to the subgroup of these viruses that lack the 3 proximal cysteine-rich protein (CRP) gene present in Allium-infecting allexiviruses. An infectious cDNA clone of WLV was constructed and a mutation introduced into the P40 gene, which is an allexivirus-specific gene of unknown function. In addition, the infectious clone was modified to express the green fluorescent protein (GFP) as an N-terminal fusion to the WLV coat protein (CP). Using this GFP overcoat strategy it was possible to follow the multiplication and movement of the virus in infected Chenopodium quinoa and spinach leaves. Introduction of the frameshift mutation into the P40 gene of WLV reduced virus accumulation by 97%, and with the GFP overcoated WLV the P40 mutation almost entirely abolished GFP fluorescence in inoculated leaves suggesting that the WLV P40 protein is required for normal levels of virus multiplication. RepositoriesWLV complete sequences deposited at GenBank. Accession Nos. MZ944847.1, OQ877124.1