What can maize teach us about plant virology?

Maize is not only a staple food crop of global importance but also host of many plant viruses of economic importance. While more challenging to work with than model hosts, there are unique aspects of maize virology that make it the perfect system to study fascinating and underexplored facets of plant virology, especially in the realm of virus-virus interactions. For instance, maize presents one of the best examples of viral synergy: maize lethal necrosis disease, which is caused by co-infection of maize with maize chlorotic mottle virus (MCMV) and a potyvirus, most often sugarcane mosaic virus (SCMV). While the exact mechanism of synergy in this system remains unknown, our group recently discovered that co-infection with MCMV can facilitate resistance-breaking by SCMV. Another unique aspect of maize is that it has non-canonical virus resistance genes and the mechanism of resistance for most of these genes is thought to be movement based – restricting viral cell-to-cell movement or systemic movement. The combination of these factors generates the intriguing hypothesis that the mechanism of resistance-breaking in this co-infection context is due to MCMV altering the movement of SCMV, a phenomenon that has been previously observed for other virus pairs but never before with the outcome of resistance breaking. This and other case studies will be presented which harness maize as a tool to understand the virus-virus interactions driving important phenotypes from the organismal to ecological scale, with important implications for disease severity, transmission, and management.