Novel Technologies for Transgenic Management for Plant Virus Resistance

Global food security is threatened by the rapidly growing human population, by plant pests and diseases, and by climate change. It is estimated that US$ 60 billion loss in crop yields (10–15% global crop yield reduction) each year is due to plant viral diseases. More importantly, viral agents are determined to be responsible for half of the emerging plant diseases worldwide. Plant virus control is accomplished mainly by chemical applications aiming at the vectors transmitting the virus to a new plant contributing to the epidemiology of the disease. The use of chemicals, in some cases, has a significant negative environmental impact and poses human risks, and thus other friendlier strategies of virus control need to be developed. Towards this direction RNA silencing (RNA interference, RNAi), a conserved endogenous pathway of all higher eukaryotes, is exploited as an antiviral method. The silencing inducer molecule is the double-stranded RNA (dsRNA) and the slicing of the target RNA is directed by specific virus-derived small interfering RNAs (vsiRNAs) in collaboration with host-encoded Argonaute enzymes. DsRNA- and artificial microRNA-mediated resistance has been exploited in transgenic plants to develop resistance against viruses. The current research efforts (computational and biochemical) focus on determining the more efficacious inducer of RNAi. In this respect, the contribution of the next-generation sequencing and bioinformatics analyses play a crucial role. The antiviral arsenal includes also the novel approach of genome editing for conferring the desired antiviral status in the host plant. This method involves less side-effects on the host gene expression as compared to RNAi related treatments. However, the DNA sequence to be modified (edited) needs to be determined in a laborious and time-consuming process prior to the actual modification. It is vital to determine the molecular/biochemical attributes in the specific plant-virus interaction that will shift the balance towards the resistance of the host to the invading virus.