Tomato spotted wilt virus Gc and N proteins interact in vivo

Tomato spotted wilt virus (TSWV) virions consist of a nucleocapsid core surrounded by a membrane containing glycoproteins Gn and Gc. To unravel the protein interactions involved in the membrane acquisition of RNPs, TSWV nucleocapsid protein (N), Gn and Gc were expressed and analyzed in BHK21 cells. Upon coexpression of Gn, Gc and N, a partial colocalization of N with both glycoproteins was observed in the Golgi region. In contrast, upon coexpression of Gc and N in the absence of Gn, both proteins colocalized to a distinct non-Golgi perinuclear region. Using FLIM and FRET, interaction was demonstrated between N and Gc, but not between N and Gn, and was only observed in the region where both proteins accumulated. The genuine character of N–Gc interaction was confirmed by its presence in purified virus and RNP preparations. The results are discussed in view of TSWV particle assembly taking place at the Golgi complex.