Galiakparov, N., Volcani Center, Department of Virology, Tolkovski Laboratory, Bet Dagan 50250, Israel, Hebrew University, Fac. Agric., Food, Environ. Qual. S., Institute of Plant Sciences, Rehovot, 76100, Israel
Tanne, E., Volcani Center, Department of Virology, Tolkovski Laboratory, Bet Dagan 50250, Israel
Mawassi, M., Volcani Center, Department of Virology, Tolkovski Laboratory, Bet Dagan 50250, Israel
Gafny, R., Volcani Center, Department of Virology, Tolkovski Laboratory, Bet Dagan 50250, Israel
Sela, I., Hebrew University, Fac. Agric., Food, Environ. Qual. S., Institute of Plant Sciences, Rehovot, 76100, Israel

A previous functional analysis of the genome of grapevine virus A (GVA) was not conclusive as to the role of open reading frame 5 (ORF 5). This ORF encodes a 10-kDa protein (p10) carrying two distinct domains: a basic, arginine-rich domain and a zinc-finger domain. P10 was cloned and expressed in Escherichia coli, and was shown by northwestern assays to interact with nucleic acids. In-frame deletion of the basic region abolished P10's nucleic acid-binding capability, whereas substitution of cysteine residues by serine in the zinc-finger domain did not affect binding. These mutations were inserted into the full-length infectious clone. It has been shown that ORF 5 mutations do not affect replication of GVA-RNA. However, plants inoculated with the aforementioned mutations did not develop symptoms, and Western blot analysis revealed markedly reduced expression of the movement protein (the product of ORF 3).