The ORF5 of Grapevine virus A is involved in symptoms expression in Nicotiana benthamiana plants

Grapevine virus A (GVA), a member of the genus Vitivirus which belongs to the family Flexiviridae, has a single-stranded RNA genome of about 7.4 kb that comprises five open reading frames (ORFs). ORF5 encodes a small 10-kDa protein (p10), which is believed to interact with nucleic acids and to suppress the plant's RNA-silencing response. We obtained molecular and biological data indicating that ORF5-encoded product, specifically its N-terminus, affects the appearance of symptoms in Nicotiana benthamiana plants. The ORF5-encoded products of the severe GR5 and the mild GTR1-1 isolates were found to affect RNA silencing similarly in mesophyll cells of N. benthamiana, despite being involved in different expressions of symptoms on this host.