Recognizing pathogen-associated molecular patterns on the cell surface is crucial for plant immunity. The proteinaceous nature of many of these patterns suggests that secreted proteases play important roles in their formation and stability. Here we demonstrate that the apoplastic subtilase SBT5.2a inactivates the immunogenicity of cold-shock proteins (CSPs) of the bacterial plant pathogen Pseudomonas syringae by cleaving within the immunogenic csp22 epitope. Consequently, mutant plants lacking SBT5.2a activity retain higher levels of csp22, leading to enhanced immune responses and reduced pathogen growth. SBT5.2 sensitivity is influenced by sequence variation surrounding the cleavage site and probably extends to CSPs from other bacterial species. These findings suggest that variations in csp22 stability among bacterial pathogens are a crucial factor in plant–bacteria interactions and that pathogens exploit plant proteases to avoid pattern recognition.

识别细胞表面的病原体相关分子模式对于植物免疫至关重要。其中许多模式的蛋白质性质表明，分泌的蛋白酶在其形成和稳定性中起着重要作用。在这里，我们证明质外体枯草酶 SBT5.2a 通过在免疫原性 csp22 表位内裂解，使细菌植物病原体丁香假单胞菌的冷休克蛋白 （CSP） 的免疫原性失活。因此，缺乏 SBT5.2a 活性的突变植物保留了更高水平的 csp22，导致免疫反应增强和病原体生长减少。SBT5.2 敏感性受切割位点周围序列变异的影响，并可能延伸到其他细菌种类的 CSP。这些发现表明，细菌病原体之间 csp22 稳定性的变化是植物-细菌相互作用的关键因素，并且病原体利用植物蛋白酶来避免模式识别。