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. In a previous study, we found that OsCERK1 is also involved in regulating copper (Cu) uptake in rice, though the underlying mechanisms remain unclear. In this study, we identified proteins that interact with OsCERK1 and discovered a novel heavy metal-associated (HMA) domain-containing protein, OsHPP08. Our findings show that OsCERK1 phosphorylates and stabilizes OsHPP08. Structural analysis using AlphaFold, a yeast sensitivity assay of the Cu uptake-deficient yeast mutant, and Cu level measurements in the oshpp08 mutants and overexpression plants ( OsHPP08OE ) revealed that OsHPP08 facilitates Cu uptake. Moreover, rice seedling infection assays demonstrated that OsHPP08 positively contributes to blast resistance, and both OsCERK1 and OsHPP08 are necessary for Cu-modulated blast resistance. Further analyses suggest that OsCERK1 and OsHPP08 likely enhance blast resistance by regulating the antioxidant system and increasing the accumulation of H 2 O 2 . In conclusion, OsCERK1 promotes Cu uptake by stabilizing OsHPP08, and together they contribute to Cu-modulated blast resistance likely by modulating ROS accumulation. These results deepen our understanding of the interplay between biotic and abiotic signals in rice.