OsMAPK6 Phosphorylates and Degrades OsCATA to Regulate H2O2 Homeostasis Conferring Resistance to Bacterial Blight in Rice.

Abstract

Mitogen-activated protein kinase (MAPK) cascades have been extensively reported to be involved in biotic and abiotic stress processes by regulating hydrogen peroxide (H₂O₂) homeostasis in plants. However, the detailed mechanisms by which MAPK cascades regulate H₂O₂ homeostasis in response to bacterial pathogens in rice remain largely unknown. Here, we demonstrate that rice CATALASE A (OsCATA) is a new substrate of OsMAPK6 and negatively regulates rice resistance to Xanthomonas oryzae pv. oryzae (Xoo) by directly suppressing H₂O₂ accumulation. Our results showed that OsMAPK6 interacts with OsCATA and specifically phosphorylates it at serine 460. The phosphorylation of OsCATA by OsMAPK6 attenuates OsCATA accumulation and reduces its catalase activity in vitro. The OsMAPK6-overexpressing (OsMAPK6-OE) plants showed lower catalase activity and higher accumulation of H₂O₂ compared with wild-type plants. The oscata mutant plants generated by the clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) strategy showed higher accumulation of H₂O₂ and increased resistance to Xoo. Together, these results suggest that the OsMAPK6-OsCATA module is involved in modulating rice H₂O₂ homeostasis and immunity.