The TaLYK5-TaDSK2a module serves as a molecular switch between plant growth and immunity during fungal attack.

Plants are constantly challenged by pathogenic microorganisms that threaten growth and survival. While the individual signaling pathways involved in these immune responses have been well characterized, how plants balance growth with rapid pathogen perception and immune signal transduction remains largely unclear. Here, we report that the receptor-like kinase TaLYK5 receptor of wheat (Triticum aestivum) recognizes chitin on the fungal pathogen Puccinia striiformis f. sp. tritici (Pst) and initiates a cascade of events that increase immune response while reducing growth. TaLYK5 acts as a positive regulator of defense by phosphorylating the ankyrin-repeat-containing protein TaAKR2A, which supports reactive oxygen species (ROS) production and defense responses. In parallel, activated TaLYK5 negatively regulates growth responses by phosphorylating serine residue S234 in the ubiquitin-binding protein TaDSK2a, blocking its ability to degrade TaLYK5. Without infection by Pst, TaAKR2A does not initiate ROS signaling and immune responses and TaDSK2a associates with polyubiquitin chains on TaLYK5 to mediate its degradation, suppress TaLYK5-mediated plant defense. Meanwhile, TaDSK2a regulates gibberellin (GA) accumulation to promote plant growth, possibly by accelerating the degradation of TaEUI, a GA-deactivating enzyme. These findings demonstrate that the TaLYK5-TaDSK2a module functions as a molecular switch that dynamically regulates the trade-off between plant immunity and growth.