VIRUS INDUCED GENE SILENCING IN WHEAT: A REVIEW

Wheat is a human food crop of high economic value and future improvements in wheat breeding require in depth knowledge of gene functions. The hexaploid genome, large genome size and recalcitrance to transformation of the cultivated wheat limit the use of functional approaches such as mutagenesis, T-DNA knockout libraries, T-DNA activation tagging or transposon gene-tagging for gene identification. Wheat functional genomics has benefitted from approaches based on post-transcriptional gene silencing (PTGS) and RNAi (RNA interference) has been deployed as an effective reverse genetics tool (involving expression knock down) to elucidate the function of wheat genes. Despite its demonstrated usefulness, RNAi in wheat cannot yet be applied to large scale projects, as it requires the generation of transgenic lines which is a time consuming and labour intensive procedure in wheat. As an alternative, virus-induced gene silencing (VIGS) has emerged as an attractive option for rapid generation of gene knock-down phenotypes to assess function of target genes. VIGS is based on homology dependent gene silencing achieved by delivery of viral RNA or DNA containing a gene fragment with homology to an endogenous gene into plants. VIGS is of great importance in wheat as it can potentially speed up the characterization of candidate genes. In this chapter, we detail virus induced gene silencing in wheat, discussing different case studies where VIGS use has been demonstrated. The benefits and drawbacks of VIGS strategy as well as its future potential to characterize plant genes controlling different agronomically important traits are also discussed.

Keywords: barley stripe mosaic virus, monocots, powdery mildew genes, virus induced gene silencing, wheat