The role and regulation of programmed cell death in plant-pathogen interactions

It is commonly known that animal pathogens often target and suppress programmed cell death (pcd) pathway components to manipulate their hosts. In contrast, plant pathogens often trigger pcd. In cases in which plant pcd accompanies disease resistance, an event called the hypersensitive response, the plant surveillance system has learned to detect pathogen-secreted molecules in order to mount a defence response. In plants without genetic disease resistance, these secreted molecules serve as virulence factors that act through largely unknown mechanisms. Recent studies suggest that plant bacterial pathogens also secrete antiapoptotic proteins to promote their virulence. In contrast, a number of fungal pathogens secrete pcd-promoting molecules that are critical virulence factors. Here, we review recent progress in determining the role and regulation of plant pcd responses that accompany both resistance and susceptible interactions. We also review progress in discerning the mechanisms by which plant pcd occurs during these different interactions.