OsCPK12 phosphorylates OsCATA and OsCATC to regulate H2O2 homeostasis and improve oxidative tolerance in rice

Calcium-dependent protein kinases (CPKs), the best-characterized calcium sensors in plants, regulate many aspects of plant growth and development as well as plant adaptation to biotic and abiotic stresses. However, how CPKs regulate the antioxidant defense system remains largely unknown. We previously found that impaired function of OsCPK12 leads to oxidative stress in rice with more H2O2, lower CAT activity, and lower yield (Wang et al., 2019). Here we explored the roles of OsCPK12 in oxidative tolerance in rice. Our results show that OsCPK12 interacts with and phosphorylates OsCATA and OsCATC at Ser11. Knock out of either OsCATA or OsCATC leads to an oxidative stress phenotype accompanied by higher accumulation of H2O2. Overexpressing mimic phosphorylated OsCATAS11D and OsCATCS11D in oscpk12-cr reduced the level of accumulated H2O2. Moreover, OsCATAS11D and OsCATCS11D show enhanced catalase activity both in vivo and in vitro. OsCPK12 overexpressing plants exhibited higher catalase (CAT) activity as well as higher tolerance to oxidative stress. Our findings demonstrate that OsCPK12 affects CAT enzyme activity by phosphorylating OsCATA and OsCATC at Ser11 to regulate H2O2 homeostasis, thereby mediating oxidative tolerance in rice.