Apoptotic cell death is a common response to pathogen attack in oats

We have examined the characteristics of cell death induced by pathogen infection in oats with respect to following hallmark apoptotic features: DNA laddering, chromatin condensation, and electron microscopic-terminal deoxynucleotidyl transferase-mediated UTP end labeling positive response. A wide range of plant pathogens representing different levels of parasitism in susceptible and resistant interactions were used for the inocula, which include (i) an obligate parasite, Puccinia coronata f. sp. avenue (the crown rust fungus); (ii) a facultative biotroph parasite, Magnaporthe grisea (the blast fungus); (iii) pathogenic bacteria, Pseudomonas syringae pv. atro-purpurea and P syringae pv. coronafaciens (the halo or stripe blights of oats); and (iv) Ryegrass mottle virus. Surprisingly, any of the pathogens used induced most of the apoptotic features in oat cells at and around the infection sites, indicating that apoptotic cell death is a common phenomenon in oats during pathogen attack. The localization and the timing of apoptotic cell death during a course of infection were, however, quite different depending on the interactions (compatible or incompatible) and the pathogens (fungi, bacteria, or viruses). Possible roles of apoptotic cell death in the susceptible and resistant interactions are discussed.