Viruses as Mutualists

Although most plant viruses are thought of as antagonists, or pathogens, this understanding is biased by the overwhelming focus of the literature on viruses that cause disease in crop plants.  In biodiversity studies of viruses in wild plants we find very few, if any, that cause disease.  Even acute plant viruses that are responsible for disease epidemics in nearby crops are found in wild plants without producing symptoms.  In addition, the majority of viruses in wild plants are not acute, but persistent, and may behave as epigenetic elements, providing increased genetic resources for plants, especially under stress.  In a related study we found that acute viruses of plants conferred drought tolerance in all virus-host combinations tested, and in some cases viruses also conferred tolerance to cold stress.  These studies are providing new insights into virus-host relationships, and will likely provide new tools for crop plant adaptation to stress.