The Mechanism Of Assembly And Movement Of Tospoviruses Virion In Host Plant

Tospovruses are economically important plant viruses, and caused serious diseases in many crops worldwide. This study focused on the mechanisms of assembly and movement of tospoviruses virion in the natural infection host plant and inocalated Tomato spotted wilt virus(TSWV) and Tomato zonate spot virus(TZSV), using these methods including negative staining, ultrathin section, immunogold labaling, and high pressure cryo-TEM in order to study on the mechanisms of assembly and movement of tospoviruses particles.The specific vesicles were induced in the cytoplasm of naturally diseased and artificially inoculated host plants infected with tospoviruses. Vesicles from tospoviruses diseased and inoculated plants varied in size, ranged from 50 nm to 1000 nm, with majority in 300nm-600 nm and were circular, globular and oval in shape. A part of vesicles contained virus particles. This is first dicovered the negative strand RNA plant virus induced vesicles.The assembly four sites of tospovirusess in host plant had been observed, early vesicles formed in the membranes of endoplasmic reticulum(ER) system, and used as the sites of assembly of virus particles. Ultrathin sections revealed virus particle assembly sites in the Golgi complex, vironplasm(VP) and filamentous inclusions(FI). Four types of aggregation of mature virus particles in the vesicles, i.e. singly particle aggregate(SPA), double particles aggregates(DPA), triple particles aggregates(TPA) and multiple particles aggregates(MPA), and most of particles agaregated in the vesicles.There were three types of intracellular movement of tospoviruses, viral particles movement along the membranes of ER, vesicles contanining viral particles movement along the membranes of ER, vesicles containing viral particles combined with other vesicles movement inside the large vesicle of cytoplasm.Based on the large numbers of observation of ulturalthin section, the viral particle-like found in the cellwall of host cells infected with tospoviruses, and NSm, NSs, Gn of TZSV and TSWV were localized in the cellwall, suggested the vesicles containing viral particles passed through the cellwall, maybe had a new pathway of cell-to-cell movement of tospoviruses infection.Based on the results of this study, host plant infected tospoviruses induced specific vesicles, and these vesicles were as roles of asemmbly, maturation, agaregation of tospovirus paticles, and regulated intracellular movement of viral paticles, maybe also regulated intercellulae movement of tospoviruses particles.