OsCERK1 Interacts with OsHPP08 to Regulate Copper Uptake and Blast Resistance in Rice

The cell surface receptor chitin elicitor receptor kinase 1 (CERK1) is a well-known component of plant immunity. OsCERK1 is involved in regulating copper (Cu) uptake in rice, though the underlying mechanisms remain elusive. In this study, we identified proteins interacting with OsCERK1 and uncovered a novel heavy metal-associated domain-containing protein, OsHPP08. Our findings demonstrate that OsCERK1 phosphorylated and stabilized OsHPP08. Through structural analysis using AlphaFold, a yeast sensitivity assay of the Cu uptake-deficient yeast mutant, and Cu level measurements in oshpp08 mutants and overexpression plants (OsHPP08OE), we revealed that OsHPP08 facilitated Cu uptake. Additionally, rice seedling infection assays demonstrated that OsHPP08 positively contributed to blast resistance, with both OsCERK1 and OsHPP08 being essential for Cu-modulated blast resistance. Further analyses suggested that OsCERK1 and OsHPP08 likely enhanced blast resistance by regulating the antioxidant system and increasing H₂O₂ accumulation. In conclusion, OsCERK1 promoted Cu uptake by stabilizing OsHPP08, and together they contributed to Cu-modulated blast resistance, likely through the modulation of reactive oxygen species accumulation. These findings deepen our understanding of the intricate interplay between biotic and abiotic signals in rice.