TaCIPK10 interacts with and phosphorylates TaNH2 to activate wheat defense responses to stripe rust

Calcineurin B-like interacting protein kinase (CIPKs) has been shown to be required for biotic stress tolerance of plants in plant-pathogen interactions. However, the roles of CIPKs in immune signalling of cereal crops and an in-depth knowledge of substrates of CIPKs in response to biotic stress are under debate. In this study, we identified and cloned a CIPK homologue gene TaCIPK10 from wheat. TaCIPK10 was rapidly induced by Puccinia striiformis f. sp. tritici (Pst) inoculation and salicylic acid (SA) treatment. In vitro phosphorylation assay demonstrated that the kinase activity of TaCIPK10 is regulated by Ca²⁺ and TaCBL4. Knockdown TaCIPK10 significantly reduced wheat resistance to Pst, whereas TaCIPK10 overexpression resulted in enhanced wheat resistance to Pst by the induction of defense response in different aspects, including hypersensitive cell death, ROS accumulation and pathogenesis-relative genes expression. Moreover, TaCIPK10 physically interacted with and phosphorylated TaNH2, which was homologous to AtNPR3/4. Silencing of TaNH2 in wheat resulted in enhanced susceptibility to the avirulent Pst race, CYR23, indicating its positive role in wheat resistance. Our results demonstrate that TaCIPK10 positively regulate wheat resistance to Pst as molecular links between of Ca²⁺ and downstream components of defense response and TaCIPK10 interacts with and phosphorylates TaNH2 to regulate wheat resistance to Pst.