Abrogation of disease development in plants expressing animal antiapoptotic genes

An emerging topic in plant biology is whether plants display analogous elem ents of mammalian programmed cell death during development and defense agai nst pathogen attack. In many plant-pathogen interactions, plant cell death occurs in both susceptible and resistant host responses. For example, speci fic recognition responses in plants trigger formation of the hypersensitive response and activation of host defense mechanisms, resulting in restricti on of pathogen growth and disease development. Several studies indicate tha t cell death during hypersensitive response involves activation of a plant- encoded pathway for cell death. Many susceptible interactions also result i n host cell death, although it is not clear how or if the host participates in this response. We have generated transgenic tobacco plants to express a nimal genes that negatively regulate apoptosis, Plants expressing human Bcl -2 and Bcl-xl, nematode CED-9, or baculovirus Op-IAP transgenes conferred h eritable resistance to several necrotrophic fungal pathogens, suggesting th at disease development required host-cell death pathways. In addition, the transgenic tobacco plants displayed resistance to a necrogenic virus. Trans genic tobacco harboring Bcl-xl with a loss-of-function mutation did not pro tect against pathogen challenge. We also show that discrete DNA fragmentati on (laddering) occurred in susceptible tobacco during fungal infection, but does not occur in transgenic-resistant plants. Our data indicate that in c ompatible plant-pathogen interactions apoptosis-like programmed cell death occurs. Further, these animal antiapoptotic genes function in plants and sh ould be useful to delineate resistance pathways. These genes also have the potential to generate effective disease resistance in economically importan t crops.