Apoptosis and disease in plants

The hypersensitive response (HR) of plants to pathogenic infection involves a form of programmed cell death, but the molecular mechanisms remain unclear. In the June 5 Proceedings of the National Academy of Sciences, Dickman et al. describe the use of transgenic plants expressing known anti-apoptotic genes from animals to explore the role of apoptosis in host defence (Proc Natl Acad SciUSA 2001, 98:6957-6962). They generated tobacco plants expressing human bcl-2, human bcl-xl, nematode ced-9 or baculovirus op-iap. All of the transgenes conferred resistance to fungal phytopathogens and to tomato spotted wilt virus. The anti-apoptotic transgenes also inhibited DNA laddering (a marker of apoptosis) following tobacco plant infection with necrotrophic fungi. This 'comparative pathobiology' approach demonstrates that plant-pathogen interactions induce cell death that resembles animal apoptosis. These transgenic plants will be important to studies of the mechanisms of plant cell death and to the development of disease-resistant crops.