Transient gene expression of antisense RNA and coat protein-encoding sequences reduced accumulation of cherry leafroll virus in tobacco protoplasts.

Cherry leafroll nepovirus (CLRV) is the causative agent of blackline disease, which results in a fatal necrosis of the graft union of English walnut scion on certain rootstocks. Tobacco suspension cell protoplasts were electroporated with plasmid constructions, bearing or not bearing RNA-derived sequences, and, subsequently, were electroporated with CLRV virions or virion RNA Replication of CLRV in protoplasts was demonstrated by accumulation of both positive- and negative-sense CLRV genomic RNAs 1 and 2, capsid antigen, and virions. Three plasmids were tested for antiviral action. These have inserts that were derived from the coat protein gene, inserted in both orientations, and from the 3' terminal sequence that is nearly identical in RNA 1 and RNA 2, oriented for expression of antisense RNA. Plasmids were introduced into protoplasts 12 hr prior to introducing the virions or virion RNA. CLRV accumulation was reduced significantly by prior electroporation of plasmids intended to express coat protein or 3' antisense RNA, but not by electroporation of plasmid without insert or plasmid with coat protein encoding sequences in the antisense orientation. These results demonstrate the utility of transient expression in a protoplast system for comparing the efficacy of a variety of virus-derived and other sequences for their potential application in virus control strategies.