Use of dsRNA in Crop Improvement

Over recent years, many crops have benefited from the application of genetic transformation approaches to improve important agronomic and horticultural traits. The discovery of RNA-mediated gene silencing (RNA silencing) has allowed the application of precise approaches to inhibit plant pathogens and to alter plant metabolism and development. RNA silencing is initiated by double-stranded RNA (dsRNA) leading to sequence homology-dependent translational inhibition of a target mRNA or transcriptional repression of a target gene. RNA silencing was first described in plants as post-transcriptional gene silencing (PTGS), virus cross-protection and co-suppression. Activated by the presence of short dsRNA inside the cell, RNA silencing is a form of negative gene regulation lending itself towards the generation of loss-of-function genetic changes. Applications include reducing gene expression of a pathogen, such as a virus; reducing the expression of an endogenous plant gene to alter biosynthesis, such as that of an undesired allergen, toxin or flower or fruit pigment; reducing the expression of an endogenous plant gene to alter nutritional qualities, such as altered starch content and reducing the expression of endogenous genes to alter plant development. Alteration of plant phenotypes and inhibiting plant pathogens through the direct application of dsRNA to crop plants has provided a rapid and efficient method that is feasible for some situations and has the advantage of avoiding the steps in plant transformation and regeneration. In this chapter, we review examples that outline the technology for the application of dsRNA in crops, and discuss the role this has played in crop improvement.