My work has concentrated on an effort to dissect the signal transduction pathways controlling programmed cell death (PCD) and to determine its role in plant defense against pathogens. We have developed a pathogen-free model system based on the response of Arabidopsis thaliana to a purified fungal toxin, fumonisin B1 (FB1). In Arabidopsis FB1 causes formation of necrotic lesions that resemble plant pathogen-induced lesions in many respects. Working with Tsuneaki Asai, we have used an Arabidopsis leaf mesophyll protoplast system to quantitatively examine PCD in defense-related mutants and to characterize the signal transduction pathway(s) controlling FB1-induced PCD. We have also taken a genetic approach to identify Arabidopsis mutants resistant to FB1-induced PCD. These studies are aimed at expanding our basic understanding of the molecular mechanisms controlling cell death in plants.