N-myristoylation-mediated shuttling of TaMP from plasma membrane to chloroplasts increases wheat susceptibility to rust fungi.

Chloroplasts are significant generators of reactive oxygen species and are crucial for plant immunity. However, how these subcellular organelles detect external stimuli and initiate specific immune responses remains largely unknown. Here we identified a plasma membrane (PM)-anchored N-myristoylated protein, TaMP, which detaches from the PM and relocalizes to chloroplasts upon exposure to pathogen-associated molecular patterns. We also uncovered a secreted protease from the rust fungus, Puccinia striiformis f. sp. tritici, that hijacks and promotes TaMP relocalization, increasing wheat susceptibility to rust fungus. In chloroplasts, TaMP interacts with TaClpS1, an adaptor subunit of the Clp protease complex. TaMP-TaClpS1 interaction enhances TaClpS1 binding to TaGluTR, promoting its degradation. Critically, TaGluTR positively regulates wheat stripe rust resistance by increasing accumulation of tetrapyrrole intermediates and enhancing retrograde signalling. However, TaMP attenuates TaGluTR function by promoting its degradation, ultimately impairing wheat resistance to pathogens. Overall, this study reveals a novel and specific susceptibility mechanism in which a rust fungus effector triggers the relocalization of a host protein from the PM to the chloroplasts to suppress organellar immune functions.