|Lim, Hyoun - UNIV OF ILLINOIS|
|Yu, Jun - IOWA STATE UNIV|
|Ko, Tae - UNIV OF MINNISOTA|
Submitted to: American Society for Virology Meeting
Publication Type: Abstract Only
Publication Acceptance Date: April 19, 2004
Publication Date: June 21, 2004
Citation: Lim, H.S., Yu, J.M., Ko, T.S., Hartman, G.L., Domier, L.L. 2004. Expression of soybean mosaic virus (smv) hc-pro intransgenic plants effects rna levels and symptom severity of bean pod mottle virus and smv. American Society for Virology Meeting; 2004. Technical Abstract: Infection of a plant by more than one virus often results in a synergistic interaction that produces symptoms more severe than infection by either virus alone. The synergism observed between Soybean mosaic virus (SMV) and Bean pod mottle virus (BPMV) significantly enhances the titers of BPMV antigens and RNAs, while SMV titers remain unchanged. In order to investigate the mechanism of this synergism, transgenic soybean plants expressing SMV helper component-protease (HC-Pro) were developed. Transgenic soybean plants expressing different levels of HC-Pro were identified using real-time RT-PCR and inoculated with a mild isolate of BPMV. Symptoms in the BPMV-inoculated plants were most severe in the transgenic line expressing the highest level of HC-Pro and mildest in the nontransformed line. Similarly, BPMV RNAs accumulated to the highest level in the line that expressed the highest level of HC-Pro and the lowest levels in the nontransformed line. When inoculated with SMV, all HC-Pro expressing lines had symptoms more severe than the nontransgenic controls at 10 days after inoculation. As with BPMV, symptom severity was related to HC-Pro expression levels in the transgenic lines. Starting at 20 days after inoculation however, new leaves of the transgenic line that expressed the highest level of HC-Pro no longer showed symptoms and SMV RNA titer was drastically reduced. In soybean lines that expressed lower levels of HC-Pro, symptoms remained severe at all sampling dates and no reductions in SMV RNA titers were observed. These data show that SMV HC-Pro is sufficient to induce the synergistic symptoms observed in plants infected with BPMV and SMV and that, when expressed at high levels, HC-Pro transgenes are susceptible to virus-induced gene silencing.