THE CYTOPATHOLOGY OF TOSPOVIRUS - HOST-PLANT INTERACTIONS

R.H. Lawson, M.M. Dienelt, H.T. Hsu
Plant cells infected with tospoviruses contain variable arrays of virus inclusions and modified host membranes. These reflect the complexity of the viral genome and particle structure as well as involvement of plant intracellular membranes in virion maturation. The mature virion is enclosed by a single envelope with two viral-encoded glycoproteins (G1 and G2) and is located within membraneous cisternae, including those of the rough or smooth endoplasmic reticulum (rER or sER). The viral core contains three single-stranded RNAs, nucleocapsid (N) protein, and a polymerase. N protein is also located in viroplasm and nucleocapsid aggregates that may be adjacent to, or associated with, rER, sER, Golgi stacks, and modified host membranes referred to as paired parallel membranes. Nonstructural movement (NSm) protein can be identified, prior to virion formation, in plasmodesmata and in nucleocapsid aggregates. A nonstructural (NSs) protein, of unknown function, is located in filamentous inclusions and in the cytoplasm. Filamentous inclusions are distinguished by appearance as Type I for tomato spotted wilt virus (TSWV) and Type II for impatiens necrotic spot virus (INSV). With this exception, the most prominent cytopathological distinctions between tospovirus isolates relate to differences in particle maturation. Budding at smooth intracellular membranes yields double membrane-bounded structures interpreted as immature virions. Outer membranes of immature virions fuse with each other and with host cisternal membranes to release mature single-enveloped virions into cisternal spaces. Maturation is accompanied by proliferation and modification of Golgi stacks, vesicles, and ER. Infections of defective and partially defective tospovirus isolates contain viroplasm, nucleocapsid aggregates, immature virions, or abnormal virionlike particles rather than mature virions. As additional tospovirus species and isolates are identified, new variations in cytopathology can be expected.
Lawson, R.H., Dienelt, M.M. and Hsu, H.T. (1996). THE CYTOPATHOLOGY OF TOSPOVIRUS - HOST-PLANT INTERACTIONS. Acta Hortic. 431, 267-290
DOI: 10.17660/ActaHortic.1996.431.24
https://doi.org/10.17660/ActaHortic.1996.431.24
https://doi.org/10.17660/ActaHortic.1996.431.24
431_24
267-290
 

Acta Horticulturae