Tospovirus

A Viral Biorealm page on the family Tospovirus

Baltimore Classification

Group V (negative sense ssRNA)

Higher order categories

Bunyaviridae

Species

Tomato spotted wilt virus (TSWV); Impatiens necrotic spot virus (INSV); Watermelon silver mottle virus (WSMoV)

Description and Significance

Tospoviruses are enveloped viruses that infect plants. An extremely wide variety of plants are susceptible to tospoviruses, including tomatoes, watermelon, peanuts, groundnuts, and flowers such as irises, impatiens, lilies, and orchids (Jones, 2005).

Genome Structure

The tospovirus genome consists of three ssRNA molecules. The molecules are simply known as L (Large), M (Medium), and S (Small). The entire genome codes for six proteins via five different open reading frames (ORFs). The L RNA encodes the virus' RNA-dependent RNA polymerase in its complement. The M RNA encodes two envelope precursor glycoproteins (G1 & G2) and a viral movement protein (NSm). The S RNA encodes the nucleoprotein (N) and a non-structural protein (NSs). The M and S RNAs are special, in that both are ambisense, meaning that one gene is encoded in the negative sense and another gene is encoded in the positive sense (Cortez et.al., 2001). The RNA molecules are capable of forming pseudo-circular panhandle structures, as well as stable hairpins, due to the presence of complementary terminal sequences (Dong et.al., 2008).

Virion Structure of a Tospovirus

The tospovirus virion consists of a quasi-spherical capsid particle 80-120 nm in diameter containing the ssRNA genome. The paritcle is enclosed in an envelope (Cortez et.al., 2001).

Reproductive Cycle of a Tospovirus in a Host Cell

Tospovirus enters the cell via an insect vector

Viral Ecology & Pathology

The tospovirus insect vector is the thrip, a small, winged herbivore. Thrips acquire the virus as larvae and transmit the virus as adults (Jones, 2005). Common insect vectors include Thrips and Frankliniella species.

Upon infection, the virus induces tissue necrosis resulting in spots and streaks on leaves and discolored rings and spots on fruits (EPPO, 2004). Symptoms may vary, depending on factors such as cultivation method, age of the plant, nutritional and environmental conditions, and the virus species and/or serotype (EPPO, 2004).

References

Cortez, I., J. Saaijer, K.S. Wongjkaew, A.M. Pereira, R. Goldbach, D. Peters, & R. Kormelink. "Identification and characterization of a novel tospovirus species using a new RT-PCR approach." Archives of Virology 146 (2001): 265-278.

Dong, J.H., X.F. Cheng, Y.Y. Yin, Q. Fang, M. Ding, T.T. Li, L.Z. Zhang, X.X. Su, & Z.K. Zhang. "Characterization of tomato zonate spot virus, a new tospovirus in China." Archives of Virology" 153 (2008): 855-864.

Jones, D.R. "Plant viruses transmitted by thrips." European Journal of Plant Pathology 113 (2005): 119-157.

Page authored for BIOL 375 Virology, September 2008