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

January 2008 , Volume 98 , Number  1
Pages  45 - 50

A. E. Whitfield, N. K. K. Kumar, D. Rotenberg, D. E. Ullman, E. A. Wyman, C. Zietlow, D. K. Willis, and T. L. German

First, third, fifth, and eighth authors: Department of Entomology, University of Wisconsin, Madison 53706; second, fourth, and sixth authors: Department of Entomology, University of California, Davis 95616; seventh author: Department of Plant Pathology, University of Wisconsin and U.S. Department of Agriculture, Vegetable Crops Research Unit, Madison, WI 53706.

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Accepted for publication 10 August 2007.

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 GN (GN-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 GN-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 GN-S mixed with purified virus and individual insects were assayed for transmission. We found that GN-S reduced the percent of transmitting adults by eightfold. In a second study, thrips were given an AAP on GN-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 GN-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.

Additional keywords:Bunyaviridae, plant virology, Thysanoptera, virus entry, virus--vector interactions, western flower thrips.

© 2008 The American Phytopathological Society