AUTHOR=Dangol Sarmina , Nguyen Nam Khoa , Singh Raksha , Chen Yafei , Wang Juan , Lee Hyeon-Gu , Hwang Byung KooK , Jwa Nam-Soo 

TITLE=Mitogen-Activated Protein Kinase OsMEK2 and OsMPK1 Signaling Is Required for Ferroptotic Cell Death in Rice–Magnaporthe oryzae Interactions

JOURNAL=Frontiers in Plant Science

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.710794

DOI=10.3389/fpls.2021.710794

ISSN=1664-462X

ABSTRACT=<p>Mitogen-activated protein kinase (MAPK) signaling is required for plant cell death responses to invading microbial pathogens. Iron- and reactive oxygen species (ROS)-dependent ferroptotic cell death occurs in rice (<italic>Oryza sativa</italic>) during an incompatible rice–<italic>Magnaporthe oryzae</italic> interaction. Here, we show that rice MAP kinase (OsMEK2 and OsMPK1) signaling cascades are involved in iron- and ROS-dependent ferroptotic cell death responses of rice to <italic>M. oryzae</italic> infection using <italic>OsMEK2</italic> knock-out mutant and <italic>OsMEK2</italic> and <italic>OsMPK1</italic> overexpression rice plants. The OsMPK1:GFP and OsWRKY90:GFP transcription factor were localized to the nuclei, suggesting that OsMPK1 in the cytoplasm moves into the nuclei to interact with the WRKY90. <italic>M. oryzae</italic> infection in Δ<italic>Osmek2</italic> knock-out plants did not trigger iron and ROS accumulation and lipid peroxidation, and also downregulated <italic>OsMPK1, OsWRKY90, OsRbohB</italic>, and <italic>OsPR-1b</italic> expression. However, 35S:<italic>OsMEK2</italic> overexpression induced ROS- and iron-dependent cell death in rice. The downstream MAP kinase (<italic>OsMPK1</italic>) overexpression induced ROS- and iron-dependent ferroptotic cell death response to virulent <italic>M. oryzae</italic> infection. The small-molecule ferroptosis inhibitor ferrostatin-1 suppressed iron- and ROS-dependent ferroptotic cell death in 35S:<italic>OsMPK1</italic> overexpression plants. However, the small-molecule inducer erastin triggered iron- and lipid ROS-dependent, but <italic>OsMEK2</italic>-independent, ferroptotic cell death during <italic>M. oryzae</italic> infection. Disease (susceptibility)-related cell death was lipid ROS-dependent, but iron-independent in the Δ<italic>Osmek2</italic> knock-out mutant during the late <italic>M. oryzae</italic> infection stage. These combined results suggest that <italic>OsMEK2</italic> and <italic>OsMPK1</italic> expression positively regulates iron- and ROS-dependent ferroptotic cell death, and blast disease (susceptibility)-related cell death was ROS-dependent but iron-independent in rice–<italic>M. oryzae</italic> interactions.</p>