Reduction of OsMPK6 activity by a R89K mutation induces cell death
Dongfei Wang+ · Hong Wang+ · Qunen Liu+ · Ranran Tu · Xingpeng Zhou · Yingxin Zhang· Weixun Wu · Ping Yu ·Daibo Chen · Xiaodeng Zhan · Liyong Cao*· Shihua Cheng* · Xihong Shen*
Plant Cell Reports
10.1007/s00299-021-02679-4
Abstract
Key message The R89 is essential for the kinase activity of OsMPK6 which negatively regulates cell death and defense
response in rice.
Abstract Mitogen-activated protein kinase cascade plays critical roles in various vital activities, including the plant immune
response, but the mechanisms remain elusive. Here, we identified and characterized a rice lesion mimic mutant osmpk6
which displayed hypersensitive response-like lesions in company with cell death and hydrogen peroxide hyperaccumulation.
Map-based cloning and complementation demonstrated that a G702A single-base substitution in the second exon of
OsMPK6 led to the lesion mimic phenotype of the osmpk6 mutant. OsMPK6 encodes a cytoplasm and nucleus-targeted
mitogen-activated protein kinase and is expressed in the various organs. Compared with wild type, the osmpk6 mutant
exhibited high resistance to the bacterial pathogen Xanthomonas oryzae pv. oryzae (Xoo), likely due to the increased ROS
production induced by flg22 and chitin and up-regulated expression of genes involved in pathogenesis, as well as activation
of SA and JA signaling pathways after inoculation. By contrast, the OsMPK6-overexpression line (OE-1) was found to be
susceptible to the bacterial pathogens, indicating that OsMPK6 negatively regulated Xoo resistance. Furthermore, the G702A
single-base substitution caused a R89K mutation at both polypeptide substrate-binding site and active site of OsMPK6,
and kinase activity assay revealed that the R89K mutation led to reduction of OsMPK6 activity, suggesting that the R89 is
essential for the function of OsMPK6. Our findings provide insight into a vital role of the R89 of OsMPK6 in regulating
cell death and defense response in rice.