A gene with ancient protein kinase and transcription factor fusion provides broad spectrum resistance against diverse races of a wheat fungal pathogen
Crop disease resistance (R) genes encode proteins with diverse protein domain architectures. The mechanisms behind the broad-spectrum resistance provided by a new class of intracellular R genes with protein kinase fusions (PKFs) remain unclear. We characterized two R genes from wild wheat, Sr39 and Sr32, which encode allelic variants of an ancient PKF involving the CBP60-Like (PKCL1) transcription factor (TF). Both protein kinase and CBP60-like domains are essential for immunity. PKCL1 provides resistance to nearly all 143 tested wheat stem rust isolates without triggering a hypersensitive response. Upon infection, PKCL1 translocates from the endoplasmic reticulum to the nucleus, likely triggered by distal systemic signaling. Expression and TF binding profiling suggests that PKCL1 induces responses though pathways partially regulated by key plant immunity activators, including the CBP60 TFs. Our results indicate that PKCL1 likely enables connections to central immunity pathways lost during wheat evolution, conferring resistance against diverse pathogen isolates.