抄録
Rapid production of reactive oxygen species (ROS) has been implicated in the regulation of innate immunity in plants. We found that two MAPK cascades, MEK2-SIPK and cytokinesis-related MEK1-NTF6, are involved in the induction of NbRBOHB (Respiratory Burst Oxidase Homolog B), an inducible form of the NADPH oxidase at the transcriptional level in Nicotiana benthamiana. In addition, we have isolated a potato calcium-dependent protein kinase (StCDPK5) that activates an NADPH oxidase StRBOHB by direct phosphorylation of its N-terminal region. The transgenic potato plants that carry a constitutively active StCDPK5 driven by a pathogen-inducible promoter of the potato showed high resistance to late blight pathogen Phytophthora infestans accompanied by HR-like cell death and H2O2 accumulation in the attacked cells. In contrast, these plants showed high susceptibility to early blight necrotrophic pathogen Alternaria solani, suggesting that oxidative burst confers high resistance to biotrophic pathogen, but high susceptibility to necrotrophic pathogen. We discuss roles of nitric oxide (NO) and ROS in basal defense against biotrophic and necrotrophic pathogens.
