Abstract: There is provided a method of inhibiting gene expression by locating a 5?-5 donor splicing site sequence in the 3? UTR of a gene or within coding sequence containing the stop codon of a gene. Stability of homologous mRNA in trans is also adversely affected leading to a reduction in expression. A polynucleotide containing a 5?-donor splicing site sequence in either coding sequence containing the stop codon or the 3? UTR is also provided and in one embodiment is in the form of a vector. The 5?-donor splicing site sequence can be present in multiple copies, for example as a tandem repeat. In one embodiment the 5-donor splicing site sequence has the sequence 5?-MAGGTRAGTA-3? where M is A or C and R is A or G.

Abstract: A novel VIGS vector is described based on pGR106. The vector includes a nucleotide silencing sequence which is homologous or complementary to a target gene of a host cell. The vector can induce gene silencing in whole plants and microplants and is also effective in the tubers of Solanum spp.

Abstract: Virus-based expression vectors carrying sequences corresponding to endogenous host genes trigger silencing through a homology-dependent RNA degradation mechanism. Virus-induced gene silencing (VIGS), is useful as a reverse-genetic tool for use in functional genomic programs for loss-of-function transient assays-based screening. Described herein is an approach to enhance the robustness of the VIGS phenotype by increasing the level of dsRNA molecule production.