Three‐dimensional analysis of membrane structures associated with tomato spotted wilt virus infection.

To study viral infection, the direct structural visualization of the viral life cycle consisting of virus attachment, entry, replication, assembly and transport is essential. Although conventional electron microscopy (EM) has been extremely helpful in the investigation of virus–host cell interactions, three‐dimensional (3D) EM not only provides important information at the nanometer resolution, but can also create 3D maps of large volumes, even entire virus‐infected cells. Here, we determined the ultrastructural details of tomato spotted wilt virus (TSWV)‐infected plant cells using focused ion beam scanning EM (FIB‐SEM). The viral morphogenesis and dynamic transformation of paired parallel membranes (PPMs) were analyzed. The endoplasmic reticulum (ER) membrane network consisting of tubules and sheets was related to viral intracellular trafficking and virion storage. Abundant lipid‐like bodies, clustering mitochondria, cell membrane tubules, and myelin‐like bodies were likely associated with viral infection. Additionally, connecting structures between neighboring cells were found only in infected plant tissues and showed the characteristics of tubular structure. These novel connections that formed continuously in the cell wall or were wrapped by the cell membranes of neighboring cells appeared frequently in the large‐scale 3D model, suggesting additional strategies for viral trafficking that were difficult to distinguish using conventional EM. Summary statement: The infection of Tospovirus induces spectacular membrane modification in plant host. In present study, systematic analyses of the modification of membrane structures in tomato spot wilt virus (TSWV)‐infected plant cells were carried out by focus ion beam‐scanning electron microscopy method, of which results revealed the information on the viral life cycle. The assembly of virion was related to the modified Golgi apparatus. The intracellular traffic of virus was related to tubular shaped endoplasmic reticulum (ER) cisternae. Fusion of ER‐virus complex to plasma membrane was observed, which was related to the release of virion to extracellular matrix. A novel membrane packaged long tubular structure was observed in connecting the endocytic vesicles and the inner components of the cell, which may relate to the intercellular movement of virus. Based on these structural information, a working model was proposed on the morphogenesis and intracellular and intercellular transport of TSWV in infected plant cells. [ABSTRACT FROM AUTHOR]