The movement proteins (NSm) of distinct tospoviruses peripherally associate with cellular membranes and interact with homologous and heterologous NSm and nucleocapsid proteins

Tospovirus is the only genus containing virus species which infect plants in the Bunyaviridae family. The aims of this study were to understand the in vivo membrane association of the movement protein (NSm) of the tospovirus species Bean necrotic mosaic virus, Chrysanthemum stem necrosis virus, Tomato chlorotic spot virus and Tomato spotted wilt virus and the homologous and heterologous interactions among NSm and nucleocapsid protein (N). The results obtained by bimolecular fluorescence complementation (BiFC) assay and chemical treatments after membrane fractionation revealed that the four NSm proteins are associated with the biological membranes with the N- and C-termini oriented to the cytoplasm. BiFC analysis for protein-protein interactions showed: i) dimer formation for all NSm and N proteins; ii) interaction between NSm and the cognate N and iii) heterologous interactions between the NSm and N proteins. The implications of these interactions in the life cycle of tospoviruses are discussed.