MAP Kinase OsMEK2 and OsMPK1 Signaling for Ferroptotic Cell Death in Rice- Magnaporthe oryzae Interactions

Mitogen-activated protein kinase (MAPK) signaling is required for plant cell death responses to invading microbial pathogens. Ferric ions and reactive oxygen species (ROS) accumulate in rice () tissues undergoing cell death during infection. Here, we report that rice MAP kinase (OsMEK2 and OsMPK1) signaling cascades are involved in iron- and ROS-dependent ferroptotic cell death responses of rice to infection. OsMEK2 interacted with OsMPK1 in the cytoplasm, and OsMPK1 moved from the cytoplasm into the nucleus to bind to the OsWRKY90 transcription factor. expression may trigger OsMPK1-OsWRKY90 signaling pathways in the nucleus. Avirulent infection in mutant rice did not trigger iron and ROS accumulation and lipid peroxidation, and also downregulated , , , and expression. However, overexpression induced ROS-and iron-dependent cell death in rice during infection. The downstream MAP kinase () overexpression induced ROS- and iron-dependent ferroptotic cell death in the compatible rice-. interaction. These data suggest that the OsMEK2-OsMPK1-OsWRKY90 signaling cascade is involved in the ferroptotic cell death in rice. The small-molecule inducer erastin triggered iron- and lipid ROS-dependent, but -independent, ferroptotic cell death in mutant plants during infection. Disease-related cell death was lipid ROS-dependent and iron-independent in the mutant plants. These combined results suggest that and expression positively regulates iron- and ROS-dependent ferroptotic cell death via OsMEK2-- signaling pathways, and blast disease (susceptibility)-related cell death was ROS-dependent but iron-independent in rice- interactions.