A Self‐Cleavage–Dependent Activation Mechanism of the Effector RipBH Associated With Bacterial Wilt and Tuber Rot in Potato

ABSTRACT Homeostatic regulation of proteolytic activity is fundamental to plant cellular physiology, and dysregulated protease‐like activities are frequently associated with cytotoxic or stress‐induced cell death. Here, we identify RipBH, a previously uncharacterized type III‐secreted protein from Ralstonia solanacearum , as an intracellular self‐cleaving protease‐like effector with the capacity to perturb host physiological balance. RipBH harbors a papain‐like catalytic core and multiple ankyrin repeats; structural mutagenesis showed that conserved catalytic residues (C135, H244, D268, and N117) are indispensable for self‐processing and cell death–inducing activity. RipBH undergoes auto‐cleavage inside plant cells, producing smaller fragments that are detectable in both the cytoplasm and nucleus. Truncation of ankyrin repeats altered cleavage behavior and abolished cell‐death induction, supporting the idea that ankyrin‐mediated structural constraints function as a regulatory module required for activation. Importantly, RipBH‐induced necrosis occurred largely independently of the tested canonical ETI‐related signaling components, suggesting a physiology‐centered disruption pathway rather than immune receptor‐mediated recognition. We propose that RipBH operates as a pathogen‐encoded proteolytic switch that destabilizes intracellular homeostasis, providing a potential mechanistic link between effector auto‐processing and necrosis‐like physiological collapse under biotic stress. Our findings contribute to the conceptual framework of proteolysis‐associated plant cell dysfunction and highlight pathogen‐driven interference with core physiological processes.