Expression of the movement protein of tomato spotted wilt virus in the insect vector Frankliniella occidentalis.

Tomato spotted wilt virus (TSWV) is able to infect both its botanical hosts and its insect vector (thrips). In plant tissue the NSM protein of TSWV functions as viral movement protein (MP), aggregating into plasmodesma-penetrating tubules to establish cell-to-cell movement. As upon heterologous expression NSM was able to form similar tubules on the surface of insect (Spodoptera frugiperda) cells, we have now investigated the expression and cellular manifestation of this protein in infected thrips tissue. It is shown that NSM, though detectably expressed in both the L2 larval and adult thrips stages, does not aggregate into tubules, indicating that this requirement is associated to its function as MP in plants, and raising the question if NSM has a function at all during the insect life cycle of TSWV

The nonstructural NSm protein of tomato spotted wilt virus induces tubular structures in plant and insect cells.

The expression and subcellular location of the 33.6-kDa nonstructural protein NSm of tomato spotted wilt virus (TSWV) was analyzed inNicotiana rusticaplants and protoplasts as a function of time. Immunofluorescent studies in protoplasts isolated from TSWV-infectedN. rusticaleaves showed that this protein could first be detected close to the periphery of the cell, near the plasmamembrane, and later in tubular structures emerging from the cell surface.In situ,these tubules appeared specifically in the plasmodesmata, suggesting their involvement in cell-to-cell movement of the virus during systemic infection. In protoplasts transfected with an expression vector containing the NSm gene, similar tubules were formed, indicating that NSm has the ability to form these structures in the absence of other virus-specific components. To test whether plant-specific components were involved in tubule formation, the NSm gene was also expressed in a heterologous expression system, i.e., insect cells.Spodoptera frugiperdaandTrichoplusia nicells were infected with a recombinant baculovirus expressing the NSm-gene (AcNPV/NSm). The efficient formation of NSm-containing tubules emerging from the surface of both cell types indicate that no plant-specific cell structures or proteins are involved in their development

Expression of the movement protein of tomato spotted wilt virus in the insect vector Frankliniella occidentalis.

Tomato spotted wilt virus (TSWV) is able to infect both its botanical hosts and its insect vector (thrips). In plant tissue the NSM protein of TSWV functions as viral movement protein (MP), aggregating into plasmodesma-penetrating tubules to establish cell-to-cell movement. As upon heterologous expression NSM was able to form similar tubules on the surface of insect (Spodoptera frugiperda) cells, we have now investigated the expression and cellular manifestation of this protein in infected thrips tissue. It is shown that NSM, though detectably expressed in both the L2 larval and adult thrips stages, does not aggregate into tubules, indicating that this requirement is associated to its function as MP in plants, and raising the question if NSM has a function at all during the insect life cycle of TSWV

Tomato spotted wilt virus particle morphogenesis in plant cells

A model for the maturation of tomato spotted wilt virus (TSWV) particles is proposed, mainly based on results with a protoplast infection system, in which the chronology of different maturation events could be determined. By using specific monoclonal and polyclonal antisera in immunofluorescence and electron microscopy, the site of TSWV particle morphogenesis was determined to be the Golgi system. The viral glycoproteins G1 and G2 accumulate in the Golgi prior to a process of wrapping, by which the viral nucleocapsids obtain a double membrane. In a later stage of the maturation, these doubly enveloped particles fuse to each other and to the endoplasmic reticulum to form singly enveloped particles clustered in membranes. Similarities and differences between the maturation of animal-infecting (bunya)viruses and plant-infecting tospoviruses are discussed