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A Versatile Assay for the Identification of RNA Silencing Suppressors Based on Complementation of Viral Movement

July 2008 , Volume 21 , Number  7
Pages  879 - 890

Jason G. Powers,1 Tim L. Sit,2 Feng Qu,3 T. Jack Morris,3 Kook-Hyung Kim,4 and Steven A. Lommel2

1Department of Genetics, North Carolina State University, Box 7614, Raleigh, NC 27695-7614, U.S.A.; 2Department of Plant Pathology, North Carolina State University, Box 7342, Raleigh, NC 27695-7342, U.S.A.; 3School of Biological Sciences, University of Nebraska-Lincoln, Lincoln, NE 68588-0666, U.S.A.; 4Department of Agricultural Biotechnology, Seoul National University, Seoul 151-921, Korea

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Accepted 20 March 2008.

The cell-to-cell movement of Turnip crinkle virus (TCV) in Nicotiana benthamiana requires the presence of its coat protein (CP), a known suppressor of RNA silencing. RNA transcripts of a TCV construct containing a reporter gene (green fluorescent protein) (TCV-sGFP) in place of the CP open reading frame generated foci of three to five cells. TCV CP delivered in trans by Agrobacterium tumefaciens infiltration potentiated movement of TCV-sGFP and increased foci diameter, on average, by a factor of four. Deletion of the TCV movement proteins in TCV-sGFP (construct TCVΔ92-sGFP) abolished the movement complementation ability of TCV CP. Other known suppressors of RNA silencing from a wide spectrum of viruses also complemented the movement of TCV-sGFP when delivered in trans by Agrobacterium tumefaciens. These include suppressors from nonplant viruses with no known plant movement function, demonstrating that this assay is based solely on RNA silencing suppression. While the TCV-sGFP construct is primarily used as an infectious RNA transcript, it was also subcloned for direct expression from Agrobacterium tumefaciens for simple quantification of suppressor activity based on fluorescence levels in whole leaves. Thus, this system provides the flexibility to assay for suppressor activity in either the cytoplasm or nucleus, depending on the construct employed.

Additional keywords:IVIS Lumina, p8, p9, pPZP212, VSR.

© 2008 The American Phytopathological Society