Rapid Determination of Gene Function by Virus-induced Gene Silencing in Wheat and Barley

The cereal crops are essential components to the human and animal food supply. Solutions to many of the problems challenging cereal production will require identification of genes responsible for particular traits. Unfortunately, the process of identifying gene function is very slow and complex in crop plants. In wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.), this process is made very difficult by the very large size and complexity of their genomes and the difficulty with which these crops can be genetically transformed. Additionally, the polyploidy of wheat greatly complicates any approach based on mutational analysis because functional, homeologous genes often mask genetic mutations. Virus-induced gene silencing (VIGS) is an important new tool that overcomes many of these obstacles and promises to greatly facilitate the assessment of gene function. A VIGS system based on barley stripe mosaic virus (BSMV) has recently been developed for use in wheat and barley. The BSMV-VIGS system allows researchers to switch-off or "knockdown" the expression of chosen genes so that the gene's function may be inferred based on the knockout phenotypes. This article describes the characteristics of the BSMV-VIGS system, relates examples of its application for functional genomics in wheat and barley, and discusses the strengths and weaknesses of this approach.