Satellites as Viral Biocontrol Agents

Despite the evidence that certain viral satellites do not encode any functional product, they can either induce specific disease symptoms or alter (exacerbate or attenuate) symptoms that helper viruses induce in some hosts. Viral satellites that attenuate symptoms have the potential to be used as viral biocontrol agents. Satellite RNAs associated with cucumber mosaic virus (CMV) are well known for viral-symptom modulation properties, and in several instances ameliorative CMV satellites have been exploited to protect plants against hypervirulent CMV strains carrying satellite RNAs molecules that are necrogenic in tomato. Preinoculation and transgenesis of ameliorative CMV satellite variants have been tested under experimental and field conditions with encouraging results, but with a warning for potential risks for the spontaneous change of an ameliorative satRNA to a pathogenic variant and its dissemination by aphids.