Immunodetection and subcellular localization of the proteins encoded by ORF 3 of grapevine viruses A and B

Polyclonal antisera were raised to Escherichia coli-expressed ORF3 products (putative move ment proteins) of Grapevine virus A (GVA) and Grapevine vir us B (GVB) (genus Vitivirus), and used for their immunodetection in infecte d plants. Western blot analysis of subfractionated cellular compartments sh owed that the distribution of both proteins was comparable to that of plant virus movement proteins, as they were transiently present in a crude membr ane fraction and accumulated in a cell wall-enriched fraction. The GVA ORF3 -encoded protein, but not the comparable GVB protein, was also present in l arge amount in a cytoplasmic soluble fraction. Intracellular immunogold lab elling localized these proteins in the cell wall and plasmodesmata of infec ted cells and, especially for GVA, in association with cytoplasmic virus ag gregates.