Puccinia triticina Effector Pt3863 Targets and Subverts TaRLCK176 to Suppress Wheat Resistance to Leaf Rust

Wheat leaf rust, caused by Puccinia triticina, is a widespread economically important wheat disease. During infection, P. triticina secretes effectors proteins to manipulate host immunity. Here we identified and characterized the P. triticina effector Pt3863, which is highly expressed during the early phase of infection and significantly enhances fungal virulence. We also identified the wheat receptor-like cytoplasmic kinase TaRLCK176 as a target of Pt3863. Functional assays demonstrated that TaRLCK176 positively regulates wheat resistance against leaf rust and is required for chitin-induced reactive oxygen species (ROS) accumulation. Pt3863 subverts this defence through a dual inhibitory mechanism: first, it suppresses TaRLCK176 phosphorylation; second, it promotes TaRLCK176 degradation via the ubiquitin-26S proteasome pathway. Host-induced gene silencing Pt3863 attenuated P. triticina virulence, while its overexpression in transgenic wheat lines increased susceptibility to P. tritici. Conversely, virus-induced gene silencing of TaRLCK176 compromised wheat resistance. Our findings establish TaRLCK176 as a critical immune hub that positively modulates wheat resistance to leaf rust and is specifically targeted by the P. triticina effector Pt3863. Notably, Pt3863 has evolved a sophisticated virulence strategy to simultaneously disrupt both the phosphorylation-mediated activation and proteasomal stability of TaRLCK176, thereby impairing host immune responses. This study elucidates a key molecular mechanism underlying the suppression of wheat immunity by P. triticina and highlights TaRLCK176 as a promising candidate target for the genetic engineering of durable resistance in wheat against leaf rust.