Virus-induced gene silencing in plants.

The Sainsbury Laboratory, John Innes Centre, Colney Lane, Norwich NR4 7UH, UK.
Methods (Impact Factor: 3.64). 09/2003; 30(4):296-303. DOI: 10.1016/S1046-2023(03)00037-9
Source: PubMed

ABSTRACT Virus-induced gene silencing (VIGS) is a technology that exploits an RNA-mediated antiviral defense mechanism. In plants infected with unmodified viruses the mechanism is specifically targeted against the viral genome. However, with virus vectors carrying inserts derived from host genes the process can be additionally targeted against the corresponding mRNAs. VIGS has been used widely in plants for analysis of gene function and has been adapted for high-throughput functional genomics. Until now most applications of VIGS have been in Nicotiana benthamiana. However, new vector systems and methods are being developed that could be used in other plants, including Arabidopsis. Here we discuss practical and theoretical issues that are specific to VIGS rather than other gene "knock down" or "knockout" approaches to gene function. We also describe currently used protocols that have allowed us to apply VIGS to the identification of genes required for disease resistance in plants. These methods and the underlying general principles also apply when VIGS is used in the analysis of other aspects of plant biology.

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    ABSTRACT: Striga hermonthica is a hemiparasitic weed that infects cereals in Sub Sahara Africa (SSA) resulting in up to 100% grain yield loss. This significant loss in grain yields is a major contributor to food insecurity and poverty in the region. Current strategies to control the parasite are costly, unavailable and remain unpracticed by small-scale farmers, underscoring the need for more economical and sustainable control strategies. Development of resistant germplasm is the most sustainable strategy in the control of S. hermonthica, but is constrained by paucity of resistance genes for introduction into crop germplasm. RNA interference (RNAi) has potential for developing host-derived resistance against S. hermonthica by transformation of host crops with RNAi sequences targeted at critical Striga genes. The application of RNAi in management of S. hermonthica is however constrained by lack of efficient high throughput screening protocols for the candidate genes for silencing, as well as sub optimal delivery of siRNAs into the parasite. In comparison to stable transformation, viral induced gene silencing (VIGS) is a rapid and powerful tool for plant functional genomics and provides an easy and effective strategy in screening for putative candidate genes to target through RNAi. In addition, VIGS allows for a secondary amplification of the RNAi signal increasing the siRNA threshold and facilitates siRNA transport through viral movement proteins. We tested the efficiency of the Tobacco rattle virus (TRV1 and TRV2) VIGS vectors in silencing S. hermonthica phytoene desaturase (PDS) gene through agrodrench and agro-infiltration.
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