|Qu, Feng - UNIVERSITY OF NEBRASKA|
|Morris, T. J. - UNIVERSITY OF NEBRASKA|
Submitted to: American Society for Virology Meeting
Publication Type: Abstract Only
Publication Acceptance Date: March 1, 2007
Publication Date: July 15, 2007
Citation: Young, B.A., Qu, F., Morris, T., Stenger, D.C., French, R.C. 2007. The P1 protein, not HC-Pro, of Wheat streak mosaic virus is a suppressor of RNA silencing. American Society for Virology, 26th Annual Meeting, Corvallis, OR, July 2007, (abstracts of meeting not published). Technical Abstract: HC-Pro, a well-characterized multi-functional protein encoded by members of the genus Potyvirus, has been shown to be involved in aphid transmission, replication maintenance, systemic movement, and posttranscriptional gene silencing (PTGS) suppression, and to be a determinant of disease synergism in mixed infections with heterologous viruses. The HC-Pro cistron of Wheat streak mosaic virus (WSMV), a member of the genus Tritimovirus in the family Potyviridae is required for semi-persistent transmission by eriophyid mites but has been shown to be dispensable for productive systemic infection in wheat and maize. Further, a HC-Pro deletion mutant of WSMV retained the ability to cause a synergistic disease of maize when co-inoculated with Maize chlorotic mottle virus and did not suppress PTGS in Agrobacterium co-infiltration assays, suggesting that a protein other than HC-Pro may be involved in suppression of PTGS. Each of the eight other proteins encoded by WSMV isolate Sidney 81 were transiently expressed in Nicotiana benthamiana 16c leaves by Agrobacterium infiltration along with a 35S-GFP construct to assay for PTGS suppression activity. Only one WSMV protein, P1, was found to suppress PTGS by this assay . P1 proteins from another strain of WSMV and from Oat necrotic mottle virus, another member of the genus Tritimovirus, also suppressed RNA silencing. Symptoms induced by Potato virus X were more severe in transgenic N. benthemiana expressing WSMV P1 than in control plants, suggesting WSMV P1 can act as a pathogencity enhancer in a heterologous system. In addition, we tested HC-Pro and P1 proteins of Agropyron mosaic virus and Hordeum mosaic virus, which are members of the genus Rymovirus. HC-Pro, but not P1, from these two viruses had PTGS suppression activities. These findings indicate that RNA silencing suppressor function arose at least two times during the evolution of the family Potyviridae.