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

Authors

Takayuki Shindo, Max Planck Institute for Plant Breeding Research
Farnusch Kaschani, Max Planck Institute for Plant Breeding Research
Fan Yang, University of Nebraska-LincolnFollow
Judit Kovács, University of Szeged
Fang Tian, University of Nebraska-Lincoln
Jiorgos Kourelis, University of Oxford
Tram Ngoc Hong, Max Planck Institute for Plant Breeding Research
Tom Colby, Max Planck Institute for Plant Breeding Research
Mohammed Shabab, Max Planck Institute for Plant Breeding Research
Rohini Chawla, Max Planck Institute for Plant Breeding Research
Selva Kumari, Max Planck Institute for Plant Breeding Research
Muhammed Ilyas, Max Planck Institute for Plant Breeding Research
Anja C. Hörger, Max Planck Institute for Plant Breeding Research
James R. Alfano, University of Nebraska-LincolnFollow
Renier A. L. van der Hoorn, Max Planck Institute for Plant Breeding Research

Date of this Version

2016

Citation

Shindo T, Kaschani F, Yang F, Kovács J, Tian F, Kourelis J, et al. (2016) Screen of Nonannotated Small Secreted Proteins of Pseudomonas syringae Reveals a Virulence Factor That Inhibits Tomato Immune Proteases. PLoS Pathog 12(9): e1005874.

Comments

© 2016 Shindo et al. This is an open access article distributed under the terms of the Creative Commons Attribution License

Abstract

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.