The first triple gene block protein of peanut clump virus localizes to theplasmodesmata during virus infection

The subcellular localization of the first triple gene block protein (TGBp1) of peanut clump pecluvirus (PCV) was studied by subcellular fractionation and immunogold cytochemistry using TGBp1-specific antibodies raised against a fusion protein expressed in and purified from bacteria. In the inoculate d and apical leaves of virus-infected Nicotiana benthamiana, TGBp1 localize d to the cell wall and P30 fractions. Electron microscopy of immunogold-dec orated ultrathin sections of the infected leaf tissue revealed TGBp1-specif ic labeling of the plasmodesmata joining mesophyll cells. In longitudinal s ections of the plasmodesmata, the TGBp1-specific labeling was most commonly associated with the plasmodesmal collar region. In transgenic N. benthamia na, which constitutively expressed TGBp1, no TGBp1-specific immunogold labe ling of plasmodesmata was observed, but plasmodesmata were gold decorated w hen the transgenic plants were infected with a TGBp1-defective PCV mutant, indicating that factors induced by the virus infection target and/or anchor the transgene TGBp1 to the plasmodesmata. (C) 1999 Academic Press.