Tandem Kinase WTK1 Triggers Waves of Transcriptional Reprogramming Underlying Wheat Resistance to Stripe Rust

Tandem kinases are emerging regulators of plant immunity, but the downstream defense programs they activate remain poorly understood. Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a major constraint on global wheat production. The Yr15 resistance gene, derived from wild emmer wheat, encodes the tandem kinase protein WTK1. To define the temporal basis of this resistance, we analysed resistant and susceptible near-isogenic lines across a 7-day infection time course using histopathology, ROS phenotyping, RNA sequencing, co-expression network analysis, and qRT-PCR validation. WTK1-mediated resistance limited fungal colonization, enhanced ROS accumulation, and triggered extensive transcriptional reprogramming. We identified 2509 pathogen-responsive differentially expressed genes, including 1530 genes upregulated in the resistant line, revealing an early phase enriched for ROS and Ca²⁺ signaling, autophagy-related processes, and metacaspases consistent with hypersensitive cell death observed in pathogen-invaded cells. This was followed by later defense reinforcement and metabolic reprogramming in later stages of infection, including pathogenesis-related proteins, cell-wall reinforcement, and phytoalexin biosynthesis, consistent with the confinement of Pst to localized necrotic lesions. Our results show that WTK1 triggers coordinated waves of transcriptional reprogramming and co-expression network responses during infection, providing insight into tandem kinase-mediated immunity and a framework for improving durable stripe rust resistance in wheat.