Beneficial viruses in plants: Potential for crop improvement

Plants encounter many stressful environmental factors, and plants have a variety of mechanisms to cope with stress.   However, plant defense is not always enough, and is especially problematic when stress is imposed suddenly.  The beneficial effects of bacterial and fungal microbes in aiding plants in coping with both biotic and abiotic stress are well studied (Rodriguez et al., 2008; Yang et al., 2009).  However, in our work we also consider the role of viruses in mutualistic symbiosis.  Viruses of endophytic fungi are required for plant abiotic stress tolerance (Márquez et al., 2007), and plant viruses can confer tolerance to cold and drought conditions (Xu et al., 2008).  Viruses can also confer resistance to further virus infection.  These studies are showing us that the role of viruses may be largely misunderstood.  Rather than pathogens, most viruses do not have detectable negative effects on their hosts (Roossinck, 2015).  Field studies of a mutualistic fungal endophyte virus shows us that, like other mutualistic symbionts, viruses are on a continuum between antagonism and mutualism, and their position on this continuum is dependent on the environment.  Deeper understanding of the role of viruses in a healthy microbiome should inform future directions in agriculture for sustainable use of arable lands as food security becomes an ever-increasing problem throughout the world.

Marquéz et al. 2007 Science 315:513

Rodriguez et al. 2008 ISME J 2:404

Roossinck 2015 JVirol. 89:6532

Yang 2009 TIPS 14:1