Intrinsic disorder in elicitin-like effectors: Molecular shields in the arms race of biotrophic pathogens

Plant pathogens establish colonization through effector secretion to modulate host immune responses. Within bacterial effectors intrinsically disordered regions (IDRs) contribute to diverse functions and pathogenicity, but their role in effectors of phytopathogenic oomycetes remains poorly understood. Here, analysis of oomycete secretomes across lifestyles reveal widespread intrinsic disorder in secreted proteins, particularly in apoplastic elicitin and elicitin-like effectors (ELLs). Combining in vitro and in planta experiments, we show that IDRs in ELLs from the biotrophic pathogen Albugo candida reduce immune recognition, consistent with an IDR-mediated shielding mechanism. This function is transferable, as fusion of an ELL-derived IDR to the immunogenic elicitin INF1 from Phytophthora infestans abolishes its recognition. These findings identify intrinsic disorder as a functional feature of apoplastic effectors that modulates host detection and promotes pathogen fitness.