We study plant viruses. My lab has pioneered studies on small RNA viruses of the Family Tombusviridae. These are some of the smallest of viruses infecting eukaryotes. We have contributed to understanding fundamental aspects of virus assembly, RNA replication and the molecular basis of virus-host interactions. Most recently, we have been exploring mechanisms of host plant resistance in Arabidopsis to turnip crinkle virus (TCV) infection. The ability to manipulate both the viral pathogen and the host plant using molecular genetic and genomic tools makes our model system particularly suitable for the study of host-pathogen interactions at the molecular level. Expression of resistance genes (R genes) is one defensive strategy employed by plants to confer resistance to specific strains of a pathogen including viruses. R genes initiate a hypersensitive type of resistance cascade (HR) that limits systemic invasion of a pathogen. Post-transcriptional silencing of the invading RNAs directed against viral pathogens has been recognized as another general defense system in plants. The recent finding that many plant viruses encode proteins that suppress this anti-viral defense system suggests that co-evolutionary adaptation between plant defense and viral counter-defense strategies is an evolutionarily active process. Recent work from our lab has shown that both types of defensive strategies are employed by plants to counteract invasion by Turnip crinkle virus (TCV). Our research has shown that specific molecular interaction between TCV coat protein (CP) and an Arabidopsis transcription factor appears to be an essential step in triggering a specific R gene based HR response. We have also shown that systemic invasion of host plants by this virus is also promoted by the viral CP functioning as a suppressor of the host RNA silencing system. Our results demonstrate that multiple functions of the viral CP ensure systemic invasion by the virus and provide important clues toward understanding the relatively sophisticated network of defense pathways that protect plants against viral infections.
We are also involved in a project to engineer crop plants including soybean with broad spectrum resistance to viral infections. A patent is pending on this strategy. We have also been involved in the development and application of RNA plant virus vectors for transient expression of "foreign" proteins in plants. We have successfully engineered a tobacco mosaic virus based vector to express several animal viral antigens including capsid proteins of Foot and mouth disease virus (FMDV) and HIV-1.