Construction and properties of a gene-silencing vector based on Poplar mosaic virus (genus Carlavirus)

A gene-silencing vector based on a full-length genomic clone of Poplar mosaic virus (PopMV) was constructed, with coat protein and movement protein genes removed, and containing instead, the coding sequence for green fluorescent protein (GFP). This paper demonstrates that the PopMV-derived gene-silencing vector was able to silence GFP expression in GFP transgenic Nicotiana benthamiana plants. The full-length genome of an Oxford isolate of PopMV (PV275) was cloned and sequenced. A full-length PopMV clone, under transcriptional control of the 35SCaMV promoter was then constructed, and the clone was able to replicate locally in Nicotiana species. Several autonomous plant RNA and DNA viruses have been converted into vectors and implemented for virus-induced gene-silencing (VIGS) of transgenes and endogenous genes [Burton, R., Gibeaut, D., Bacic, A., Findlay, K., Roberts, K., Hamilton, A., Baulcombe, D., Fincher, G., 2000. Virus-induced silencing of a plant cellulose synthase gene. Plant Cell 12, 691-706; Dalmay, T., Horsefield, R., Braunstein, T.H., Baulcombe, D.C., 2001. SDE3 encodes an RNA helicase required for post-transcriptional gene silencing in Arabidopsis. EMBO J. 20, 2069-2077; Gossele, V., Fache, I., Meulewaeter, F., Cornelissen, M., Metzlaff, M., 2002. SVISS--a novel transient gene silencing system for gene function discovery and validation in tobacco plants. Plant J. 32, 859-866; Holzberg, S., Brosio, P., Gross, C., Pogue, G.P., 2002. Barley stripe mosaic virus-induced gene silencing in a monocot plant. Plant J. 30, 315-327; Ratcliff, F., Martin-Hernandez, A., Baulcombe, D., 2000. Tobacco rattle virus as a vector for analysis of gene function by silencing. Plant J. 25, 237-245; Ruiz, M., Vionnet, O., Baulcombe, D., 1998. Initiation and maintenance of virus-induced gene silencing. Plant Cell 10, 937-946]. The use of a virus that naturally infects trees as a gene-silencing vector has not been demonstrated before. The ability to systemically silence a plant transgene following the production of a gene-silencing signal from a locally replicating viral-construct derived from a carlavirus has not to our knowledge been shown before.