The Wheat CRK-RLCK-MAPKs Signalling Module Confers High-Temperature All-Stage Resistance to Stripe Rust

As global warming continues, rising temperatures significantly alter the interactions between wheat and the stripe rust pathogen Puccinia striiformis f. sp. tritici (Pst). Utilising high-temperature all-stage (HTAS) resistance to Pst is a novel strategy for breeding climate and disease resilient wheat cultivars. Cysteine-rich receptor-like kinases (CRKs) are involved in massive transduction pathways upon perception of biotic and abiotic stresses in plants. Here, we identify a CRK subfamily gene, TaCRK6, from Xiaoyan 6 (XY6), a wheat cultivar possessing non-race-specific and durable HTAS resistance to stripe rust. The expression of TaCRK6 concurrently responds to both Pst inoculation and the relatively high temperature treatment. Silencing TaCRK6 significantly attenuated HTAS resistance to Pst in XY6. Furthermore, overexpression of TaCRK6 in susceptible wheat cultivar Fielder exhibited a resistant phenotype with reduced Pst sporulation and increased necrosis. TaCRK6 interacts with and primarily phosphorylates the cytoplasmic kinase TaRLCK185 with the threonine residue at position 248. Notably, the MAPK signalling cascades, positioned downstream of TaRLCK185, are proved to participate in activating HTAS resistance in XY6. TaRLCK185 transduces the MAPK cascade signals by interacting with and primarily phosphorylating the serine residue of TaMAPKKK1 at position 132. TaCRK6-mediated phosphorylation of T248 alters the conformation of TaRLCK185, which in turn promotes its interaction with TaMAPKKK1, ultimately leading to activation of the downstream TaMAPKKK1-TaMAPKK9-TaMAPK6 cascade. Moreover, the TaCRK6-TaRLCK185-TaMAPKs module regulates the biosynthesis of salicylic acid (SA). These results indicate a TaCRK6-TaRLCK185-TaMAPKs module that transduces dual stress signals, coupling with the SA pathway initiation to ultimately activate HTAS resistance against Pst in XY6.