Screen of Non-annotated Small Secreted Proteins of Pseudomonas syringae Reveals a Virulence Factor That Inhibits Tomato Immune Proteases

PLoS Pathogens

Fang Tian¹  Renier A. L. van der Hoorn¹  Fan Yang¹  Judit Kovács²  Mohammed Shabab³  Jiorgos Kourelis⁴  Tom Colby⁴  Selva Kumari⁵  Tram Ngoc Hong⁵  Takayuki Shindo⁵  Muhammad Ilyas⁵  Anja C. Hörger⁵  Farnusch Kaschani⁵  James R. Alfano⁵  Rohini Chawla⁵ 

[1] Center for Plant Science Innovation and the Department of Plant Pathology, University of Nebraska-Lincoln, Lincoln, Nebraska, United States of America;Department of Plant Biology, University of Szeged, Szeged, Hungary;Mass Spectrometry Group, Max Planck Institute for Plant Breeding Research, Cologne, Germany;Plant Chemetics lab, Department of Plant Sciences, University of Oxford, Oxford, United Kingdom;Plant Chemetics lab, Max Planck Institute for Plant Breeding Research, Cologne, Germany

关键词: Proteases;    Tomatoes;    Cysteine proteases;    Apoplastic space;    Pseudomonas syringae;    Leaves;    Plant bacterial pathogens;    Pseudomonas;   

DOI  :  10.1371/journal.ppat.1005874

学科分类：生物科学（综合）

来源: Public Library of Science

【 摘 要 】

Pseudomonas syringae pv. tomato DC3000 (PtoDC3000) is an extracellular model plant pathogen, yet its potential to produce secreted effectors that manipulate the apoplast has been under investigated. Here we identified 131 candidate small, secreted, non-annotated proteins from the PtoDC3000 genome, most of which are common to Pseudomonas species and potentially expressed during apoplastic colonization. We produced 43 of these proteins through a custom-made gateway-compatible expression system for extracellular bacterial proteins, and screened them for their ability to inhibit the secreted immune protease C14 of tomato using competitive activity-based protein profiling. This screen revealed C14-inhibiting protein-1 (Cip1), which contains motifs of the chagasin-like protease inhibitors. Cip1 mutants are less virulent on tomato, demonstrating the importance of this effector in apoplastic immunity. Cip1 also inhibits immune protease Pip1, which is known to suppress PtoDC3000 infection, but has a lower affinity for its close homolog Rcr3, explaining why this protein is not recognized in tomato plants carrying the Cf-2 resistance gene, which uses Rcr3 as a co-receptor to detect pathogen-derived protease inhibitors. Thus, this approach uncovered a protease inhibitor of P. syringae, indicating that also P. syringae secretes effectors that selectively target apoplastic host proteases of tomato, similar to tomato pathogenic fungi, oomycetes and nematodes.

【 授权许可】

CC BY