A Soluble Form of the Tomato spotted wilt virus (TSWV) Glycoprotein G_N (G_N-S) Inhibits Transmission of TSWV by Frankliniella occidentalis

Abstract

Tomato spotted wilt virus (TSWV) is an economically important virus that is transmitted in a persistent propagative manner by its thrips vector, Frankliniella occidentalis. Previously, we found that a soluble form of the envelope glycoprotein G(N) (G(N)-S) specifically bound thrips midguts and reduced the amount of detectable virus inside midgut tissues. The aim of this research was to (i) determine if G(N)-S alters TSWV transmission by thrips and, if so, (ii) determine the duration of this effect. In one study, insects were given an acquisition access period (AAP) with G(N)-S mixed with purified virus and individual insects were assayed for transmission. We found that G(N)-S reduced the percent of transmitting adults by eightfold. In a second study, thrips were given an AAP on G(N)-S protein and then placed on TSWV-infected plant material. Individual insects were assayed for transmission over three time intervals of 2 to 3, 4 to 5, and 6 to 7 days post-adult eclosion. We observed a significant reduction in virus transmission that persisted to the same degree throughout the time course. Real-time reverse transcription polymerase chain reaction analysis of virus titer in individual insects revealed that the proportion of thrips infected with virus was reduced threefold when insects were preexposed to the G(N)-S protein as compared to no exposure to protein, and nontransmitters were not infected with virus. These results demonstrate that thrips transmission of a tospovirus can be reduced by exogenous viral glycoprotein.

Disrupting the Transmission of a Vector-Borne Plant Pathogen

“…Different concentrations of lectins must be used to determine when the complete saturation of putative binding sites on vectors occurs; the same is true for the blocking assays with antibodies. Similar results were observed with circulative viruses (10,32). Due to the biological complexity of biofilm establishment and development, it was expected that no individual treatment would result in the total blockage of transmission.…”

“…Molecular interactions in both of these models determine transmission success (8,12), highlighting the possibility that the disruption of such interactions leads to the blockage of transmission. In the case of circulative viruses, it has been shown that recombinant capsid proteins or peptides that bind to receptors on midgut epithelial cells of insects result in decreased transmission efficiency, presumably by masking receptors so that pathogens cannot attach to vectors (5,10,19,32). A similar approach should also work for noncirculative pathogens, where there generally is more information available on vector-pathogen interactions.…”

The NSs Protein of Tomato spotted wilt virus Is Required for Persistent Infection and Transmission by Frankliniella occidentalis

“…Data were published supporting the model of receptor-mediated endocytosis for TSWV entry, showing interaction of Gn and Gc glycoproteins with 50-kDa (10,11) and 96-kDa (12) thrips proteins, respectively, probably coordinating the entry process and circulation through the vector. Furthermore, binding of a Gn-soluble form to the thrips midgut inhibited transmission by F. occidentalis (13). The importance of the viral envelope and glycoproteins for interaction with the vector was also supported by further experimental evidence: (i) TSWV nucleocapsid preparations could not infect primary thrips cell cultures, whereas the same preparations could systemically infect mechanically inoculated plants, and (ii) thrips could not transmit an envelope-defective isolate (14).…”

Tomato Spotted Wilt Virus Benefits a Non-Vector Arthropod, Tetranychus Urticae, by Modulating Different Plant Responses in Tomato

“…The average Ct value (n = 3) obtained for the mock control for each target and reference gene was determined and used in the RER calculations. To estimate virus titer, the normalized abundance of TSWV N RNA (genomic and transcript RNA) was calculated using the Pfaffl inverse equation [48]: E ref Ctref / E N CtN as described previously [49]. …”