Plants are constantly exposed to microbial pathogens and through evolution have developed a battery of defense mechanisms for combating microbial diseases. The major research interest of our group is to decipher the regulatory network of plants defense responses. Transcriptional regulation of plant host genes is a central part of plant defense response and elucidating the complex regulatory mechanisms for the differential expression of plant genes holds the key to our understanding of the molecular basis of plant disease resistance. We are studying a family of plant transcription factors containing the novel WRKY zinc-finger DNA-binding motifs. WRKY transcription factors are found only in plants and are encoded by a large gene family with more than 70 members in Arabidopsis. A majority of the WRKY genes in Arabidopsis are rapidly induced upon pathogen infection, suggesting a major function of the gene family in plant defense responses. We are using both genetic and molecular approaches to understand the regulation and biological functions of plant WRKY genes in plant defense responses.

In addition, we are studying posttranscriptional gene regulation and its roles in plant antiviral defense. Many eukaryotic organisms contain a group of novel RNA-dependent RNA polymerases (RdRPs) that synthesize small complementary RNAs (cRNAs) using cellular or viral RNA as templates. Certain members of RdRPs have recently been shown to be required for dsRNA-mediated gene silencing (RNA interference, RNAi). Recently we have identified a new plant RdRP that is induced by viral infection and defense-inducing compounds such as salicylic acid. Plants deficient in the inducible RdRP activity become more susceptible to viral pathogens. We are interested in further understanding the biological functions of plant RdRPs and elucidating their action mechanisms in antiviral defense and RNAi.